Water tanks for the technically challenged

I was wondering if someone could help me out there. I am having trouble wrapping my head around how our rainwater tank collects water from all of our downpipes. To me it looks as if the pipe feeding the rainwater tank comes directly from the roof but how does it collect water from the other downpipes? And where is the first flush diverter supposed to be situated? Any simple explanation would be appreciated.

Hi Liliana,

Re first flush diverter what area are you in and what will the harvested rainwater be used for?

The photo shows that the infeed is from a tee fitting coming off the side of the downpipe. If a first flush diverter is fitted on the downpipe, the tank would receive water from the tee once the first flush diverter filled but if other downpipes also divert water to the tank, then there is no first flush diverter and the water diverted from the other downpipes comes up the downpipe via a wet/charged system.

Could you post a photo showing the entire tank and downpipe (or is it a first flush?) thanks?

A couple of things to be aware of...

Wet system downpipes should be fitted with leaf diverters but don't have leaf diverters that have a coarse 6-8 mm outer mesh and a mosquito proof inner mesh because the larger outer mesh will let a lot of larger debris and solid bird droppings pass through. The nutrient rich bird droppings will simply wash through but the inner mesh can dam with the larger debris and overflow when you get heavy rain as this is when most debris is washed from the roof and gutters. Buy a leaf diverter that has a fine outer mesh.

Re harvesting additional downpipes, the problem here is that this usually requires downpipes to be diverted along walls (which is ugly) or diverted by a (flooded) 'wet system'.

The other big problem is that tanks will overflow during heavy rain if the overflow pipe's capacity is less than the inflow capacity. Calculations must be made to ensure that this won't happen.

Is there a pump and if so, could you also post a photo showing the area where the pump's suction line from the tank fits to the tank and another photo that shows how the pump's suction line from the tank connects to the pump.

EDITED 13/10/22: Removed reference to a link and the link that was no longer available.

Hmm more pictures would be good.

From what I see only one down pipe is flowing into tank.

One overflow pipe coming from the tank.

The vertical pipe along the wall is the first flush.

Pulpo

Thanks SaveH2O for the very comprehensive reply and also thanks Pulpo. We are in Melbourne and the Melro 2500litre tank is supposed to provide water to the washing machine and the garden. It does fill with water but I have only just started using it and it has rained a lot in the last three months. I can't find any evidence of anything that unscrews and don't believe that we do have a first flush water diverter. I have asked the builder where it is and he hasn't replied at all. We were supposed to have a Rainbank pump and I have just discovered the cover is hiding (because you can't get it off) a completely different pump. Here are some more pictures:





















Top of the gutter with an interesting screw

So just digesting what you have said there H2O - how could our building designer have come up with a roof plan that says "All downpipes to feed RWTs located as per proposed floor plan" if there are no pipes on the walls, only downpipes?

Hi Liliana,

That was quick with the photos!

Your second photo in your last post shows that the vertical pipe under the tee is not a first flush diverter...unless they have installed some demented first flush that you can't access to open for maintenance.

If it is an inaccessible first flush (and I have seen them before, one was at a Bunnings store), then it is most probably blocked underground at the dripper and this is the only reason why water is going into the tank. I think that you have been misled re having a first flush diverter.

Re the last photo showing the screw: this is very poor workmanship. The screw makes an ideal debris trap.

The reason I wanted a photo of the pump's hose where it connects to the pump was to see whether they had connected the hose to the pump with a suitable length of straight hose to the pump's suction inlet. Many plumbers make the connection with an elbow fitted directly onto the pump's suction port, this can cause cavitation that can seriously damage the pump. The pump's suction line should respect 8 pipe diameters between an elbow and the pump's suction port but from the photo, I can't tell how close the elbow is to the pump and of course you can't take the pump cover off.

In Victoria, new 6 star homes have the option of fitting either a solar HWS or a 2,000 litre or larger rainwater tank. The tank is required to harvest a minimum of 50 square metres of roof. There are a couple of things wrong here however.

(1) In Melbourne, a house fitted with a 100 x 50mm or 90 mm round downpipe servicing the usual 23 degree pitched roof can only service a roof catchment area that is a maximum 50 square metres unless fitted with larger capacity gutters than those normally fitted.

(2) A roof area servicing one downpipe on a 23 degree pitch roof is subject to a multiplier of 1.21 to account for wind driven rain. As an example, a roof with a plan area of 40 square metres would be calculated for gutter and downpipe size as having an area of 40 x 1.21 = 48.4 square metres.

What this all means is that most rainwater tanks plumbed to new homes in Victoria do not qualify for the 6 star standard because few harvest the required roof catchment area..

For your install, one 90 mm round downpipe is highly unlikely to meet the criteria for the 6 star standard unless other downpipes are also harvested but I believe that this would be the case.


I suppose this comes down to what is actually shown on the plan despite it being stated that "All downpipes to feed RWTs located as per proposed floor plan". As explained, the watertank must be supplied from a minimum roof harvest area of 50 square metres to attain the 6 star rating.

Re the Rainbank, the plumbing regulations require you to have either an automatic or manual mains water switching device if you are on mains water and also have rainwater plumbed for sanitary flushing. The Rainbank is an expensive automatic mains water switching device but there are simpler and cheaper other devices available that also meet compliance.

Re washing machine, you have posted on another thread that the tank is buried about 130 mm. The problem is that one photo indicates that they have also buried the tank's ball valve!

EDITED 3rd July, 2013 The pump is higher than the tank's ball valve. This means that unless the pump is fitted with a check valve, the pump will drain of water when the tank level drops below the pump's suction port. You need to check if the pump is fitted with a check valve.

EDITED 13/10/22 Updated some terms used.

Wow! That's some post SaveH2O. I'd trade my camera for your knowledge about rainwater tanks any day. The reason they drilled holes in the pump cover was precisely so that we couldn't take it off and see that they hadn't installed the right pump. But my son had the idea of putting a small camera on a stick and putting it inside the hole to film what was in there!
I must admit I have just relied on our "sustainable" building designer to look after all the technical details and am now having to come to grips with the matter myself in order to ask the builder to rectify his faults. I want to be absolutely sure of what I am asking him to do before I do it. But I have just read in the CSIRO Home Energy Saving Handbook that pumps are only worthwhile if you are using the rainwater regularly in the house. As it only feeds the washing machine would a manual switch be better?

You need a pump to deliver the tankwater. The Rainbank and other similar products are devices that switch over to mains water use whenever the tank gets low. The mains water is then supplied by mains pressure to the house through the same line that the rainwater feeds through.

Do you have one or two cold water taps in the laundry?

The problem with water tank plumbing is that plumbers are not trained in this discipline and it has resulted in mass non compliance and sub standard installations. The problem is endemic Australia wide.

If the vertical pipe was installed as a first flush diverter, then it must be blocked and of course it is also inaccessible. This is the only way that I can see how water can possibly be flowing into the tank. If you tap up its length, you should be able to tell whether the pipe is full of water to the level of the horizontal pipe that feeds the tank. I have a feeling that if it is a first flush diverter, the plumber might not have known that they block and need maintenance access.

There are several issues here that include probable non compliance with the 6 star standard, sub standard tank installation (tank valves underground, uneven base, etc), goods as described not supplied and installed and non compliant plumbing (gutter pop fitted on wrong side of gutter) plus whatever a professional inspection might find.

Others on the forum may be able to advise as to a proper course of action. Is this the only thing you have had trouble with? It may be restricted to just an incredibly incompetent plumber but the blame for this ultimately rests with the Victorian Plumbing Industry Commission for failing to provide training and requiring qualifications to perform work in this field.

Once you get this sorted out, I can advise of ways that you can inexpensively and compliantly harvest a lot more better quality water plus cost effective ways to use that water.

Thanks for all that H2O. I'm going to sit down and have a good think about what you have said and I'll be very interested in discussing this matter further with you when I've finished sorting out all the problems on this build. The plumber also installed the gas hot water heater wrongly - and it was this forum that helped me out there too.

I am very sorry to hear that Liliana.

You will need to brace yourself if you start trying to take action, the building industry protects its own and there are a lot of people in the industry who are ethical bankrupts. Even the inspectors who's services use to offer protection to the consumer are now contracted by the builder. The plumbing industry is rife with incompetence and rip off artists. Do as much homework as you can and make inquiries to the various bodies beforehand. Maybe also send a pm to some of the regulars on this forum who you have judged to have to expertise and experience to be able to help with solid professional advice for your situation.

Hi Liliana,

Re your second post and your reference to the Rainbank...I just realised that you may think that the Rainbank is a pump. The rainbank is a mains water switching device that is separate to the pump. If you have a look at the photo on this link, you will see that it is a separate device. It would be interesting to know what pump you have. The Davey pump is a good pump.

http://www.davey.com.au/News/New_RainBa ... eased.aspx

The building designer put in her notes under plumbing "Rainbank pump". Another bit of confusion and carelessness then. What we actually have is a Vada V80-H pump with a Vada Rain2Main auto controller. The builder told me that is our "rainbank". Just on the subject of the downpipes all draining to the RWT, the roof plan actually only shows three downpipes feeding the RWT - so that has cleared up that confusion in my mind. So when people refer to the downpipes as being part of a "sealed system" that would be true whether we had a rainwater tank or not. I assumed that it was because they were all feeding the rainwater tank and was trying to understand how the water was getting there from all the downpipes. I'm beginning to get the hang of this. Fantastic.

Also, on the subject of the sediment to the washing machine - we actually have a Triple Action Filter from Rainharvesting at the back of the pump -it is nightime or I'd go and take another photo - so that probably takes care of the sediment.

"RainBank" is a product name and registered trademark. I notice that Reece Plumbing sell the Vada range.

The photo shows only one downpipe supplying the tank but the three downpipe "sealed system" will have two other downpipes connecting underground to the downpipe fitted with the tee. This fits the definition of a sealed system and would explain how the water feeds into the tank. Definitely no first flush diverter!

There are concerns.

Firstly and obviously, the horizontal pipe above the tank's top inlet is not fitted with a mosquito proof flap valve and other areas of the wet system allow mosquito and vermin access.

The photos show two other downpipes further down the side but neither is fitted with a mosquito proof leaf diverter, nor is the downpipe at the house. If these are the other two downpipes in the "sealed system", then mosquito proof leaf diverters should be fitted but fitting is not mandated in Victoria.

If the three downpipes shown are the mentioned "sealed system", then none have first flush diverters. These however are not a mandated requirement but which should be fitted if they are specified in the contract.

If the sealed system is as assumed, then I would have strong concerns about sediment build up in the underground pipes given the lack of leaf diverters and first flush systems as this can lead to wet pipe stagnation and blockages. This would cause a big problem if the area above the pipes was paved or concreted over.

If two other wet system downpipes have been plumbed to the tank as described, then repositioning the tank will be a bit more work than first thought. Does the plan show the plumbing from all three downpipes and does the plan show two downpipes travelling wet to the downpipe at the tank?

EDITED 13/10/22 Deleted outdated PIC link and the reference to it.

Hi again Save H2O,

Thanks for taking all this trouble to help me out. All I have is a roof plan which shows the position of the downpipes on the roof and DP to RWT for three of them. There is no plumbing plan as such to show how this is supposed to be achieved. I can't post the roof plan because of copyright but, assuming the roof plan would be of any use, I can email it to you if you pm me your email address.

PS the roofplan also shows the stormwater drain location.

So if the whole system is non-compliant, does that mean I can get an inspector from the Plumbing Commission to come and do a report on it? And why would the building surveyor pass it? Should the building surveyor not be able to see this kind of thing?

Just to answer my own question. I've just rung the Plumbing Commission and they don't inspect. It is a self-regulated industry which means that unless the consumer can work out for themselves that something is wrong there is nothing to stop plumbers giving you certificates that are meaningless! Apparently also

http://www.pic.vic.gov.au/resources/doc ... _tanks.pdf

is only a recommendation, not a regulation and there is also no regulation about inspection openings. The only thing that does make it non-compliant is the fact that, if three downpipes are feeding the one water tank, there are not enough overflows.

Hi Liliana,

I have previously had discussions with the PIC about the requirement for IOs and I have been told that they are required. The technical solution sheet that I linked states:

Cleaning and maintenance
A rain-head and strainer "is required" at the eaves gutter connection to prevent debris entering and blocking the charged downpipe.
lf the rainwater tank is to be used for drinking water, then a first flush diverter "should" also be installed. "lnspection openings must be provided" to enable regular cleaning of the below ground section (see Figure 1).

The wording ""is required", "should" and "Inspection openings must be provided" are definitive, this is why I posted that first flush diverters are not required as the document states ""should".

I have also been informed that the PIC requirements overrule the codes where there is conflict.

It depends who you talk to I suppose and this latest conflict of verbal advice is indicative once again of the state of the plumbing industry. It also demonstrates the 'head in the sand' approach that is taken when an endemic problem is not acknowledged because of the magnitude of incompetent practice that has been allowed to perpetuate unabated. This situation also exists with the large number of new homes that have non compliant roof drainage. Having the authorities acknowledge the situation would be an admittance of regulatory mismanagement by those who are entrusted to ensure compliance.

It is also extraordinary that you were told that it is a self regulated industry, do you know what they were referring to? Was it the plumbing industry or rainwater harvesting installations? The PIC provides no training to plumbers in rainwater harvesting installations yet they vigorously protect their regulated closed shop mentality by not offering specific training and accreditation to others in an industry sector that is rampant with sub standard and non compliant work. The consumers are the ones who suffer.

The PIC also claim "We audit a minimum of five per cent of each licensed plumber practitioner's work, ensuring that the relevant plumbing laws are being met. Audits are conducted by compliance auditors. Their role is to conduct on-site assessments of the work performed, against the particular compliance certificate lodged".

http://www.pic.vic.gov.au/www/html/194-audits.asp

Unfortunately, their advice that the overflow is not compliant is technically incorrect as the three downpipes discharge to the tank through a charged pipe that is the same size as the overflow pipe. This is another regulatory failure as the regulations should read (my suggestion only) "The water tank's overflow capacity must be equal to or greater than the inflow capacity"

I have sent a PM with Email address. I only need to see the downpipe locations to know the underground flow path.

As per last post, the other two downpipes have to be connected to the bottom of the downpipe at the tank as there is no other way that water from the gutter above the tank can divert water into the tank with the plain tee fitted the way it is.

The serious issue with the system is the very real potential build up of debris and the resultant possibility of a blockage or stagnation in the underground pipes. Unfortunately, this in itself does not breach compliance because this is the nature of most wet systems unless they can be regularly flushed. It is called a wet system because the pipes are always full of water to the level of the tank and the underground pipes are lower than the tank.

As per the PIC document's tank diagram I linked in my last post, a wet system (depending on who you talk to) is required to have two Inspection Openings (I.O.'s) in order to access/flush the underground pipe. If there are two other downpipes connected to the downpipe at the tank (sealed system) to feed into the tank via the tee, then the photos show that there is no I.O. fitted at the tank's downpipe as should be expected. A quick look at the other two downpipes shown on the plan might also reveal a similar story.

The absence of leaf diverters shows a lack of understanding and the requirements for a wet system as does the tank's (arguable) non compliant overflow sizing. The position of the tank's overflow outlet is also very high, this gives minimal mitigation during a storm. Some manufacturers now do this to maximise the tank's storage capacity but consumers do not realise the possible consequence of the design during heavy rainfall.

The really big problem here is that the I.O.s can be easily fitted as can leaf diverters, first flush diverters, a proper sized overflow pipe and flap valves but the inherent problem with the system will remain, that is, even with the I.O.s and everything else fitted, occasionally 'flushing' out the wet system to prevent stagnation and debris build up is near impossible as the I.O.s will be higher than the underground pipes.

It would also be good to know whether they used 90 mm stormwater pipe (86 mm internal diameter) or the more appropiate 100 mm DWV (drain, waste, vent) pipe with a 102 mm internal diameter.

The substantially cheaper 90 mm stormwater pipe is thin walled (2 mm thick) and should never be used but plumbers do bury it for wet systems as "out of sight, out of mind" applies. The more suitable and larger 100 mm DWV pipe however holds more water, therefore any flushing benefits during heavy rain are diminished as the water will travel 42% slower than the same inflow of water through the smaller pipe.

I can calculate flushing rates for varying rain intensities once I know the underground pipe size, where the two remote downpipes merge (turbulence generates sediment resuspension that facilitates more effective flushing) and the plan area of the other two roof areas harvested but the person who designed this system should have already done this.

If the three downpipe "sealed system" has been installed as I suspect and if it was me, I would be concerned about the possibility of a future underground wet system blockage if the area was paved. I have seen many blocked wet systems and the blockages look like congealed tar. I would suggest that the person who designed this system has little knowledge and experience with these systems as indicated by the absence of I.O.'s and leaf diverters. Having the ball valve that supplies the pump from the tank covered by dirt is an unforgivable lack of care.

Re building surveyors; In my experience, not many are aware of roof drainage compliance let alone rainwater harvesting systems. These days, the surveyors are contracted by the builder and this is one reason why huge numbers of new homes are passed with non compliant roof drainage.

I will give you my thoughts as to the best course of action once I see the plan but my immediate thoughts are to relocate the tank away from the window and onto a slab (it was probably buried due to the location and height of the window), have the (future) inaccessible wet pipes removed and connect the two remote downpipes to the stormwater, restore the downpipe at the tank and use a small but tall tank (they don't cost much) to collect water from one or more high yield downpipe to supply decanted water to the main tank. I can design this for you (no charge). I would have to do this by PM as the system would need to include a proprietary product to substantially reduce plumbing expenses.

The other alternative is to upgrade the system with the appropiate fittings but otherwise keep the "sealed system". I would also check as to whether the termite barrier has been compromised by the tank.

Quote:

The PIC also claim "We audit a minimum of five per cent of each licensed plumber practitioner's work, ensuring that the relevant plumbing laws are being met. Audits are conducted by compliance auditors. Their role is to conduct on-site assessments of the work performed, against the particular compliance certificate lodged".

Hmm is that seriously true?

I was on a building site in the last few weeks, the certifier identified 37 faults with the plumbing.

And I guarantee that the rain water system was not even considered for faults.
In the bush they are bit more aware of the requirements but certainly not in H20's league.

Quote:

It is a self-regulated industry which means that unless the consumer can work out for themselves that something is wrong there is nothing to stop plumbers giving you certificates that are meaningless!

And all work must be carried out by qualified plumber, (no DIY) and to buy the Australian standards to check they have done the correct job is not cheap, not to mention buying the standards for all areas of the house build would really add up.

I installed my own septic system, council wanted the system certified by a plumber so called a few plumbers; I know my install was correct but the plumber was adamant my method was wrong and needed to be changed so I pull out the standards to show it was not only according to the manufacturers recommendations but also the Australian Standards, yep he suggested he did not have time for this sH#t he was busy.

So many tradies and others bullsh@t when they don't really know and just hope the person hearing know even less.

As you and others have worked out that H20 is on the ball.

Sorry to hear you are having problems with your new home but it could be worse.

Pulpo

Hi Pulpo,

I actually only started examining my rainwater tank because the plumber installed the hot water system incorrectly. He hadn't read the installation manual at all. This forum and Rinnai themselves gave me enough information to get it sorted. There is still a problem with it though because it makes an audible noise inside the house every time you turn the water on and off. The plumber said it is the "solenoids" and "this model does that". I rang Rinnai and got him to speak to them and then he blamed the fact that we have a weatherboard house. (He has already given me a lecture on everything wrong with the design of our house and why it shouldn't have been built like this.) I am now getting the builder to book a service call through Rinnai to see if we can sort out the problem. Just in passing though - I do remember that during the build, the builder was always asking me whether I was allowed to have a rainwater tank (we are on an estate with recycled water) and he would insinuate that the plumber was going to refuse to sign off on it. It got to the point where I rang the council and asked if I was allowed to have a rainwater tank and when they said "yes" I relayed this information back to the builder who insisted he had only been joking! Now I think that the plumber didn't know how to install it and was trying to get out of it.

Not only is that true but those 5% inspections are normally close to the major cities. I worked in a rural area 150km from Melbourne for 5 years and never heard of any of the plumbers having an inspection.

Hi Liliana,

I have spent some time researching the regulations and it has been perplexing as I have found that there is a lack of regulation for rainwater tank installations in Victoria apart from general plumbing requirements. There are numerous booklets and guidelines published by various regulatory bodies but I could not find any compiled regulations although some publications claimed to have done so. I also could not find any regulatory references to water tank wet systems and they are not encompassed under the same regulations as drainage pipes. As such, I now believe that leaf diverters, IO’s and mosquito proofing of water tank wet systems are not a regulatory requirement in Victoria. I am still searching for a regulation that covers the size and/or flow requirement for a tank’s overflow pipe but even if I do find something, I already know that it will be inadequate in scope.

Click: http://archive.nwc.gov.au/__data/assets ... ersion.pdf to download a document from the National Water Commission titled: Requirements for installation of rainwater and greywater systems in Australia, Master Plumber and Mechanical Services Association of Australia, Waterlines Report Series No 10, November 2008. If you go to the Victorian section on page 25, there is basically nothing there but it does refer to the Victorian Plumbing Industry Commission Technical Solution Sheet I previously linked that contains information that states what “must” be done but I cannot find any regulations to support these directives.

The text below is copied from pages 5 and 6 in the above handbook and refers in part to Technical Solution Sheets. I for one have been previously misinformed by the PIC as to the requirements published in the plumbing technical solution sheet and my subsequent understanding was that the sheet was based on regulatory requirements. I now know that it is not and what a ridiculous situation it is for the Plumbing Industry Commission to publish a technical solution sheet that states requirements that they have not regulated. This situation is not confined to just Victoria and as seen below, the National Water Commission recognises the mess that this segment of the industry is in but the document is four years old and little has changed since.

“For installation of both rainwater and grey water systems, the approvals required, reporting needed, and responsibilities of the householder, plumber and regulatory authority (for example, councils, health departments and environment departments) vary considerably across Australia. It appears that the installation and approval process is often complicated and difficult to understand. Initially this must discourage householders and have them turn to their own resources to install rainwater or grey water system. If not installed correctly (complying with the appropriate guidelines and standards), this could ultimately compromise human health or the local environment.
A number of guidelines currently available across Australia do not provide sufficient stand-alone approval process, design, installation and maintenance details at a technical and practical level for plumbers and householders to understand what is involved, and for plumbers to install rainwater and grey water systems. There is usually some referral to several other standards, codes or guidelines.
Some states and territories have produced documents to address this issue. For example, the Rainwater plumbing guides for use and installation (SA Water 2006b) and the Sydney Water guidelines for rainwater tanks on residential properties. Plumbing requirements (Sydney Water 2003 – Amendment) are a good step in the right direction. Many other states do not provide guidance, and the guidance that exists is limited technically (especially from a plumber’s perspective of the practicalities of installing systems).
Many states or councils offer some type of government rebate to encourage use of rainwater and grey water systems, most require licensed plumbers to install them (bucketing or direct diversion of washing machine grey water doesn’t usually require a plumber). The plumber must supply evidence of installation and that it has been done to a specific standard (in many cases there is no auditing of this process). The plumbing code (AS/NZS 3500 (AS/NZS 2003b)) relates only to the diversion of septic tanks, but not to grey water systems. What specific standards should they be installed to?
Plumbers are generally identified as the interface between the user (householder) and the relevant standards, guidelines and regulations. Technical solutions for plumbers are dispersed through at least 10 Australian Standards, a number of codes, several state guidelines, two Australian guidelines and numerous acts of legislation and local government requirements.
Plumbers are a crucial link in the householders’ understanding of rainwater and grey water systems. In many cases plumbers gain the final approval and install the rainwater or grey water system. This Waterlines publication provides a national overview, and aims to facilitate a greater overall understanding of the approval, installation, maintenance and use of both grey water and rainwater for interested householders, new home builders and plumbers”.