Sludge in rain water tank

I'm trying to post a diagram on for the outlets and inlets for the tanks, to see if there are any comments, and I'm not sure if the diagram will appear:


[url=http://postimage.org/]click image upload[/url

I did a diagram of where we plan to put the inlets and outlets, but I still can't work out how to post it (I've been trying to use postimage.org). So I'll describe it in words instead:

On the west tank, the inlet would be at the 2 o'clock position; the outlet to the pump at the 3 o'clock position (I think that's too close, but not sure if we can move either much); the overflow at the 9 o'clock position and the gate valve at the base at the 10 o'clock position.

On the east tank, the inlet at 2 o'clock; the gate valve also at the base at 2 o'clock; the overflow at 6 o'clock and the outlet to the pump and to a bucket tap at 9 o'clock.

Any comments welcome

The following is (hopefully) a link to my diagram:

[img]

[/img]http://postimage.org/][/url]
click image upload

Post image asks you to select the size, what size are you selecting?

Try a larger size before selecting the image and then check the posted size on Homeone by clicking preview next to the submit button. You can always edit the post and replace the image.

Thanks, SaveH20. Hopefully this will be bigger.

Should we try and get the outlets as far away from the inlets going to the pump as we can? Is the water from the outlet dirtier if they are closer together? Does it matter where we put the overflows and the bottom outlets for garden watering in relation to the inlet?

I hope to find some time later tonight to answer the last few posts. Getting ready to go overseas at the moment.

The pump is supplied by an outlet valve. I don't understand what you are asking in the last post.

I do have some concerns re the diagram you have posted, the main one being the probable lack of access to clean the overflow mesh due to the distance from the top meshed inlet.

I am not keen on having a dry system's top meshed inlet above the outlet that supplies the pump...unless you are fitting a device like a WaterBoy. Water falling from a height can generate considerable sediment re-suspension, not what you want around the outlet that is supplying the pump.

Most tanks that I see with problems in this scenario also have the outlet valve that supplies the pump fitted very close to the bottom of the tank. I have even seen tanks manufactured with a threaded molding at the very bottom of the tank where people have no choice but to fit the outlet that supplies the pump!!!

I was trying to remember last night when I sat down to do a reply and Google searches were of no help. This morning, Promains came to mind but their website no longer comes up because the company went into liquidation last year.

http://www.smartcompany.com.au/finance/ ... apses.html

I am not 100% sure if this was the company. If anyone reading this knows how to access archive websites that are no longer shown, I would appreciate it.


No. There is plenty of information available on the internet.


Garden supplies outlet. Just break them up. They also form a protective coating after about 6 months and need to be broken again. They are used to stabilise the pH, not as a quick shock treatment.


It would only be used as an initial treatment and it wouldn't involve a huge amount.

Sodium bicarbonate, also known as sodium hydrogen carbonate and baking soda is also used to make antacid tablets.

EDIT: http://www.simplyrecipes.com/the_differ ... ng_powder/

Human blood is slightly alkaline with a pH of 7.4 and it can vary only slightly outside of this range without health problems. It is better to consume slightly alkaline water than acidic water. pH stands for "power of Hydrogen".

Various household appliances also react unfavourably to acidic water.

If you collect a water sample for any type of test, make sure that you collect it from where the pump draws the water. Most people mistakenly collect it from just under the surface.


Tests have shown that 2mm per sq m is needed to be collected after a longish period with no rain but a minimum of 0.5mm should be collected after rain events of shorter duration between the previous rain event. If you were to use the 0.5mm minimum, then you are looking at 43.5 litres for each FFD without accounting for the gutter. Even a 100mm DWV pipe (104mm ID) would require a pipe 5 metres long!


It could be the zinc, the only way you will know is to have a lab test done. Given that the foul water was collected after minimal rainfall, it must also be remembered that there would have been evaporation from the roof surface and that the collected water was concentrated.

The link below is from the University of Warwick in the UK and discusses FFDs. They have done a lot of RWH research in the past including research that mirrors my own that found that the best method of delivering water to a tank is through a bottom inlet and the best quality water to draw from is found near the surface, the opposite areas to how nearly all rainwater harvesting systems deliver and draw water.

http://www2.warwick.ac.uk/fac/sci/eng/r ... -flush.pdf

The next link is a report on a First Flush study by Brian Caughley and Stan Abbott, Senior Lecturer in Microbiology and Communicable Diseases and director of the Roof Water Research Centre at Massey University, New Zealand. The study was conducted on 560 New Zealand households over a 5 year period and it found that over 40% of the tanks had heavy faecal contamination.

http://www.pwwa.ws/pdfs/Stan_Abbott_RWH ... andout.pdf

You can read about the Massey University Roof Water Research Centre below.

http://www.massey.ac.nz/massey/learning ... c_home.cfm

Do you mean something like http://archive.org/web/

?

Thanks again for your info, SaveH2O. We'll try and get the inlets as far away from the outlets to the pump as we can.



If we are having a pipe attached to the overflow which will go down the tank and then at least 3 metres horizontally (almost) after that, do we need mosquito mesh on the tank outlet? At the end of the 3 or so metres horizontal pipe, we plan to have a T intersection or an elbow, with slotted pipe after that. Our plumber recommended an "inspection/overflow outlet" at the T or elbow, as he says sometimes such pipes can block. He could put a screw-on meshed cap on that, but said he didn't think mosquitoes could navigate a vertical pipe and get into the tank, and he's never seen them coming out of such a pipe.

Do you (or anyone else) know enough about mosquito behaviour to say whether we'd need mesh on any part of the overflow and connected pipes as described?

Thanks heaps...great site!

Yep, it was Promains, their website stated that all PVC-u pipes were chosen to conform to AS/NZS 4020 irrespective of the end use and that samples were supplied to AMS Laboratories, Silverwater NSW for testing.

It is unfortunate that this company went into liquidation. Companies that go the extra step should at least be supported by the regulations, in this instance by adherence to use of products in contact with drinking water to be certified to AS/NZS 4020.

I can absolutely guarantee you that mosquitoes will travel up open unmeshed pipes for a considerable distance. Like your plumber, I haven't seen mosquitoes coming and going out of pipes but I have seen the egg rafts floating on the water surface and the wrigglers under the surface. After first seeing this, I did some research and found many references online about this subject.


From egg to adult mosquito takes 8-10 days, depending on ambient temperatures.

So I guess that means we should have mosquito mesh on the tank overflow outlet, as I imagine it would be impractical to put it instead at the end of the overflow pipe as well as over the inspection/overflow outlet?

Another question on a different angle: We plan to use an old pressure pump, and our plumber said we might want to think about the health aspects of the rubber in its bladder perishing. So far I haven't found anything on the internet to enlighten me about this, so any info would be welcome.

Regulations state that the tank overflow must be mosquito proofed. there are also other things that can get up drainpipes.

I don't understand what an "inspection/overflow outlet" is referring to.

Sounds like the pump has a pressure tank but I would be guessing if I gave an answer to your question.

I will be away for several days, this will be my last H1 visit until I am back.

Yes it does.



We're now thinking of having a Flap Valve / Frog Flap from Rain Harvesting on the end of the overflow pipe and no slotted pipe.

Our latest dilemma is what sort of pipe to use for the downpipe from the gutter outlet to the tank's meshed inlet. We were impressed with the dimensions of 100mm (nominal) DWV pipe, and thought we might use that, but it doesn't comply with AS/NZS 4020 (re Drinking Water), and there seem to be a couple reasons why it wouldn't be suitable:

A bloke from my local hardware told me DWV pipe has root inhibitor sandwiched between the outer and inner layers of PVC in the pipe wall. The root inhibitor is dyed blue or pink, and he showed me one that had been cut, and I could see the blue circle. If the pipe is cracked or deteriorates in time, the root inhibitor chemical could leach into the water. EDIT: I now think this is a mistake – see my post 11 Aug.

And a bloke who used to work for one of the big pipe firms told me that DWV pipes use ground up recycled plastic (in the form of a foam) sandwiched between the inner and outer layers, and it wouldn't be known whether this recycled plastic had been contaminated.

So we're considering either

-having two 90mm downpipes of PVC stormwater pipe going into each tank, although we can't find any that complies with AS4020, or

-using galvanised downpipe made up to fit the Rain Harvesting Leaf Diverter and First Flush Diverter. The standard 100mm which is available off the shelf isn't quite the right size. or

-using PVC pressure pipe which is AS 4020 compliant, but which is expensive and doesn't come in very convenient sizes.

Is there any PVC stormwater pipe that's AS4020 compliant? Or any other suitable pipe?

Are there any other suggestions for downpipe (preferably bigger than 90mm) that's suitable for rainwater used for drinking?

Pressure tanks can be made with either a drinking water compliant bladder or an 'industrial' bladder. There was a cheap and popular 100 litre pressure tank sold on eBay a few years ago that was advertised as suitable for household use but people started complaining about the taste of the water. It was then found that the tank was fitted with an industrial bladder. If the plumber was referring (earlier) to the pressure tank bladder, you can have them replaced but just be aware that the replacement must be suited to purpose.

Pumps are also sold as garden and household and the prices are usually identical but some manufacturers make all of their pumps suitable for potable use. You need to check.

If you are concerned about the state of the pressure tank's bladder and if it is a small tank, you may be better off buying a larger pressure tank than replacing the bladder in the existing one.

uPVC DOWNPIPES

What you have mentioned about the root inhibitor in DWV pipes is something that I was not aware of. It certainly raises some ethical issues but the plumbing industry is not bound by ethics.

A couple of years ago, I was told during a conversation with a senior person from one of the two major uPVC pipe manufacturers in Australia that uPVC pressure pipe, stormwater pipe and DWV pipe were all made from the same material except that DWV pipe had a small amount of regrind added and stormwater pipe had a larger amount of regrind added. There was no mention of root inhibitor! Note that uPVC pressure pipe is made from virgin material and is certified to AS/NZS 4020.

On reading what you posted, I checked some DN 90mm uPVC stormwater pipe and some DN 100mm uPVC DWV pipe and found that the middle 'sandwich' of both the stormwater and DWV pipe contained the majority of both pipe's material. As to how much regrind was in each 'sandwich' , I cannot say. The DWV pipe's 'sandwich' did seem to be a very light pink/orange colour as you also indicated but I would be confident that the inner and outer uPVC sheaths are made from virgin material.

uPVC is a very strong material but the DWV inner core does raise some ethical questions when plumbed for potable water use as I have mentioned.

The practicality is this:

The only manufacturer that I knew off (Promains) who made AS/NZS 4020 certified uPVC stormwater and DWV pipe went into receivership last year. I consider this to be a blight on the plumbing industry because the regulations clearly state that pipes in contact with drinking water must be certified to AS/NZS 4020 yet there have been *tens of millions of downpipes that harvest water for potable use fitted with non compliant uPVC pipes while the company that made the compliant pipes was unsupported by the regulations and went into liquidation.
* The 2011 Census found that there were 832,100 households in Australia that were not connected to mains water.

In Victoria, the VBA technical solution sheet 4.05 Charged Systems To Rainwater Tanks states:

The pipe materials and fittings must be approved in accordance with AS/NZS 3500.1 and AS/NZS 3500.3 and be fit for purpose (either drinking or non-drinking).

The following types of materials are commonly used, however any materials used must comply with the requirements of the relevant standard.

Drinking water

Polyethylene pressure pipe to AS/NZS 4130 Polyethylene (PE) pipes for pressure applications.

PVC-U pressure pipe to AS/NZS 1477 PVC pipes and fittings for pressure applications.

AS/NZS 2032 Installation of PVC pipe systems specifies that PVC-U pressure pipes installed in
direct sunlight must be either painted with light coloured water-based paints, or otherwise protected.

For drinking water, the above listed downpipe material requirements apply whether the system is charged or not charged.

Where rainwater is to be used for drinking or human consumption, the connecting pipe material/s must comply with AS/NZS 4020 Testing of products for use in contact with drinking water. Drinking water is water that is intended and suitable for human consumption, food preparation, utensil washing or oral hygiene.

Non-drinking water

PVC-U at least DWV quality to AS/NZS 1260 PVC-U pipes and fittings for drain, waste and vent application.

uPVC stormwater, DWV and pressure pipe are all made to different nominal diameter (DN) sizes to prevent the different pipes being joined together. Using larger bored and thicker walled pressure pipe as downpipe would be expensive and not practical in any case and as you can see, the VBA solution does not offer a solution, it only states the regulations...(which were never enforced in Australia in any case)!

I will make some inquiries during the week as to whether there is another manufacturer but I am not confident.

Just an aside here, Logan City Council require the suction side of the pump to not only be pressure pipe (AS4020), but it must also be painted with UV paint.

It was one of a couple of pedantic items that got knocked back on our final plumbing inspection.

Have you heard of that before ?

AS/NZS 2032 states that uPVC pressure pipe installed in direct sunlight must be either painted with light coloured water-based paint or otherwise protected.

The Logan City Council requirement that the suction side of the pump be fitted with a uPVC pressure pipe is WRONG.

1. Many pump manufacturers recommend in their warranty conditions that a flexible coupling is used on the suction side. The reason for this is because many tanks will flex and bulge as they fill and empty. If a hard (inflexible) connection was to split, the tank could drain a considerable amount of water before it was noticed.

2. The applicable Standard is found in AS/NZS 3500.1 Section 11 PUMPS.
This section specifies requirements for the installation of pumps used in water services for buildings.

11.4 (b) states: Pumps shall-
have vibration eliminators at the base of the pump, on the suction side and the delivery side of the pump, so as to minimise the transmission of noise into the building structure and along the piping system and to prevent undue stress being placed on the pump.

Blue stripe poly pipe is commonly used on the suction and delivery side of pumps as a flexible coupling. Polyethylene is an inert plastic that is certified to AS/NZS 4020 - products in contact with drinking water.

Well it is pretty rigid, it has basically what I'd call 'meccano' pieces to hold it level with the pump inlet, and where it goes in through the top of the tank the gap around it is silicone sealed to stop moquitoes supposedly, so there's really no movement allowed on the suction side.

The silicon seal was another reason for the final inspection knockback, as it hadn't been siliconed on the first inspection.

At least if it breaks, the pump is on top of the tank, so there will be minimal loss.