Rainwater tank questions

Rainwater is naturally acidic which is great for the garden but not so for thin copper pipe. To neutralise the pH, you can add some limestone chips to a close weave nylon bag tethered to a buoy.

The copper pipe supplying the tap appears to be 12mm which will have high friction losses. If you can upsize it, you won't regret it. Of interest, a 12mm pipe has 7.2 times more friction loss than an 18mm pipe. If you can verify the internal diameters of the copper pipe and the proposed replacement pipe, I can calculate their comparison friction loss figures for you.

I have two 18mm hoses and also a short 12mm extension I can use to connect to 12mm fittings. Your biggest gain in flow to the garden would be to do the same.

What is the suction hose pipe size? An outside diameter will suffice. EDITED: Typed "section". now changed to "suction".

The Onga Pump are separate units. Are they both "broken"?

I recommend the Acquasaver mains water switching device. It works by hydraulic power, not electricity, and is usually trouble free.

Yes, you have a double whammy with having a drain valve supplying the pump and the downpipe dropping water into the tank from above that area. How old is the tank and has it ever been desludged?

It is relatively easy to desludge a tank by fitting a tee fitting to a length of 25mm pressure pipe with a 25mm faucet elbow fitted to the top. The tee will have some holes drilled in it at 7 o'clock and some 100mm lengths of capped pvc pipe fitted to the tee's run likewise. The holes in the tee need to be smaller than the holes in the pipe. You then use a 25mm poly director to connect some 25mm poly pipe (or similar) to drain to ground. Fill the poly pipe with water and then start a siphon. Desludging is best done with a full tank. A pool cleaner also works well.

If you desludge and empty the tank, you will be able to drill a higher hole for an outlet to connect to the pump. 200mm high is not much if there is a heavy sludge layer and water is being diverted to the tank above the pump supply outlet. Have you considered fitting a floating intake filter? These draw the best quality water in the tank that is 200-300 mm below the water surface and you can make one much cheaper than what the current commercial ones sell for.

The Tankvac uses an 80mm external pipe that will drain into a DN 90mm pvc stormwater pipe but I would save the money. You can make your own sediment vacuum system by fitting some pipes to an outlet and then connecting a large hose to the outlet and opening the valve for a few minutes. The holes in the pipe(s) start small and increase in size the further away from the valve they are. There is a guideline as to the number and size of the holes in relation to the suction pipe diameter.

There are videos on YouTube showing how to fit an outlet to the bottom of a tank without getting into the tank and it's always easier the second time.

You can eliminate the need to clean the overflow outlet's mesh and increase the tank's overflow capacity by fitting a twin meshed Air Gap. They are a good product.

Leaf diverters should be fitted to wet systems but not so much to a dry pipe infeed if you don't have a leaf problem. Putting some shade cloth over the top basket mesh makes cleaning the mesh much easier plus it blocks sunlight.

Your tank would have been a good candidate for our Supadiverta system.

1. Neutralising the pH is good insurance if the house also has copper pipe.
2. Plumbing 12mm copper pipes from a pump is crazy. So obviously wrong yet so common.
3. The 18mm hose and the short 12mm hose have hose connectors at both ends. The two hoses are connected by a 12mm x 18mm joiner. Far better to have larger pipes/hoses and a quality small pump than a strangled powerful pump.
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4. Blue Stripe poly pipe is measured as an outside diameter, the 25mm Blue Stripe's internal diameter is 21mm. A true 25mm internal diameter pipe has 42% more volume. It is an extremely common substandard practice to connect this size poly pipe to a pump's 1" suction port. I am assuming that the current pump's suction port is 1".
5. A well set up small, inexpensive pump will last longer and give better service than a poorly plumbed, powerful,expensive pump. All you need to do is have the correct pipe sizes (oversized are also ok), a straight run of suction hose that respects about 8 internal diameters immediately before connecting to a pump's suction port and a cross ventilated pump cover that is protected from ambient heat as high temperatures are a prime cause of capacitor failure. A capacitor is easily replaced, plenty of YouTube videos show how. A little knowledge will avoid being ripped off by an unscrupulous pump dealer. I would look at buying an Ozito pump from Bunnings. They have a 3 year warranty and a customer recently bought one with a pressure controller for less than $200 on special. A bargain! A 600W motor is more than sufficient. I think that the Ozito pumps are made by the German company Einhell. I have been meaning to find out for sure, will try to remember to do so.
6. I think it would be well worthwhile to desludge the tank. What I described in the previous post is just a rudimentary but effective vacuum cleaner of sorts.

SUPADIVERTA:
The Supadiverta utilises advanced siphonic drainage that diverts water to an inlet fitted about 100mm above the bottom of the tank. This means that the head pressure is variable because the head pressure relates to the tank's water level, not the height of a pipe above a tank. This in turn allows the use of smaller pipes and the emptier the tank is, the more head pressure there is and the higher the potential flow rate will be. PVC pressure pipes are used but these are easily converted to cheaper DWV pipes and fittings for longer runs by using female fittings connected by poly nipples which are tapered so the fit to either DWV or pvc pressure pipe fittings.
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Sorry, I can't reduce the photo size. The above is a reducing poly nipple.

The advantages to converting your system as I see it are-
1. You re-establish your downpipes.
2. You can remove the pipes currently plumbed along your walls.
3. You won't have water dropping into the tank above the drain outlet. Do you have dirty water in the cisterns?

4. If you height adjust the Supadivertas on the downpipes to match the maximum height of water you want in the tank, you won't need the tank's overflow pipe. The overflow outlet can then be capped to increase the tank's capacity. Please don't take this the wrong way but I would personally be annoyed every time I saw your tank's overflow pipe.
5. The tank will have minimal sludge but the 'sludge' will be more like a powder.
6. Your current first flush diverter's dripper has high yield loss and maintenance is almost certainly a messy chore. You will also be rid of it.
7. One advantage of only filling a tank until it is full is not having water along with any contaminants constantly being diverted into the tank. You can also close the tank's inflow valve when expecting episodes of mud rain like we had twice here in Vic about 10 years ago. That was when water tanks and swimming pools were contaminated and a week later, it happened again!
8.The middle outlet is molded below the reservoir floor level which allows the capture of any grit etc that falls throught the 750 micron internal filter throughout the entire rain event.
9. A high yield downpipe that is away from the tank and which would normally present problems to harvest can be attached to remotely when needed. My highest yield downpipe is at the house back corner and my main tank is on the opposite side near the front corner with a full length veranda across the back. The main tank harvests 3 downpipes, one next to it and others to the right and left. The one on the left is half way down the side of the house and all I did was extend the ground level pipe to the veranda's back corner and fit an inline valve and a sprinkler adaptor. A sprinkler adaptor is what fits into a hose connector. I have the same arrangement on the Supadiverta fitted to the remote downpipe and when I need more water, I simply connect one of my 18mm hoses between the two pipes.
10. The tank will be easily disconnected if ever needed as you will only need to close two ball valves and disconnect two poly nut and tails.
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18mm sprinkler adaptor.

You would be best to desludge the tank before adding the limestone because I have a feeling that it would just sit in sludge otherwise.

The pipe type and size you replace the 12mm pipe with really depends on what fits the tap. I just used 12mm - 18mm figures as an example.

It is best to have the correct size pump suction pipe because the flow rates also have to include outdoors use. An irrigation store or pond shop will usually have rolls of pressure rated, UV stabilised, flexible hose that they cut off lengths of pipe to required sizes.

The Acquasaver comes in two sizes. It can sit on the pump or away from the pump but there are probably a few things that you should have a plumber do.

The inlet size needed for the inflow depends on your roof area harvested and you area's rainfall pattern. I can advise once I know.

After you desludge the tank, you could remove the drain valve and refit it with 90 degree elbow fitted to the inside rather than drill another hole..

It depends on the style of overflow outlet you have but most overflow outlets can be capped with a cap you can buy for less than $3 at Bunnings. Just run some silicone around the contact surface to seal it. Capping the outlet increases the tank's volume.

The optional first flush diverter is manually emptied and maintance free. You can run the 19mm poly pipe into the downpipe and manually open the inline valve to drain it. Alternatively, you can drain it into a bucket and empty it on the garden.

The tank's top meshed 'bucket' inlet must retain its mesh. Water needs to breathe, leaving the mesh open (not covered by a hard lid) is best practice but it is ok to put some shade cloth over the mesh.

When you fit the Supadivertas to the downpipes at a height that allows them to serve as the tank's overflow, you can fit as many as you like because the tank will never overflow. Once the water is higher than the internal reservoir wall, the water automatically overflows to the stormwater.

You can also fit the Supadivertas at any time. By wrapping cling wrap around the filters, all water will be diverted to the stormwater until the Supadiverta is connected to the tank and the cling wrap removed. It would be best to have them fitted at the same time the downpipes are reconnected to the stormwater.

The Supadivertas all divert to a common carrier pipe that increases in size at each downpipe. The Supadivertas also regularly purge air when the reservoir water level drops below the top of the anti vortex baffles. This regularly self cleans the charged pipework.

For suburbia, it is more important to harvest as much water as reasonably possible during times of high use and low rainfall than it is to concentrate on catching the maximum amount of rain during heavy rain.

Another feature is that the carrier pipe is recharged of all friction losses at each Supadiverta because the head pressure is the same at each Supadiverta. With standard charged rain harvesting systems, the downpipes the furthest away from the tank are the first to overflow during heavy rain due to the system friction losses while the downpipes closest to the tank require less head pressure to deliver their water to the tank.

You can also have flashing made by a roll former and painted to put under the Supadiverta to hide the pipes. A customer has told me that colorbond sheet is very expensive now but he sent me a link to some much cheaper aluminium sheet that can be used. I haven't had time to follow it up yet but I will.

Re drilling a hole, if you drill a hole for a 50mm inlet for example, you don't drill a 50mm hole. The hole has to be measured to the diameter of the fitting's threads. It's a trap for new players.

I don't know if it is my computer but the photos I uploaded are only half showing. That has never happened before.

Gutters have high and low points, the high points determines the roof area that drains to each downpipe. Downpipes are (or should be) connected at the low points. The high point is easily determined by pouring water into sections of gutter and seeing which way it flows but it looks like you have high gutters. Approximations are ok but it is important that I know your area's rainfall intensity. Can you send me a PM letting me know the region you live?

There are a few reasons why a tank overtops but a common one is caused by the fine detritus that floats on the water surface during and for sometimes weeks after it rains. This fine film can and often will gum up the mosquito proof mesh. The mesh usually has an open area of about 55-60% but because the mesh has round strands which act as bellmouths, the flow restriction is about 10-15% when clean. When the mesh has a gum buildup, the flow restriction quickly increases.

To clean the mesh, you can either have access bu removing a tank's top meshed inflow basket and giving the filter a scrub. Unfortunately, numerous tanks have the meshed basket away from the overflow outlet which necessitates taking the overflow pipe off but even then, only one side of the mesh can be scrubbed.

As you know, the Australian company RaimHarvesting make an excellent dual meshed Air Gap that can also be optioned with filters that are easily removed for cleaning. I have also seen air gaps made by other companies but my philosophy is that if you can't improve on something, don't manufacture a competitor.

The only thing I will add is that it is not uncommon for an overflow pipe or its fitting to break at the top of the pipe due to either seasonal ground movement or the pvc pipe expanding and contracting during seasonal weather changes. To avoid this if the overflow pipe is 90mm pvc, home owners can fit either an expanding joint or expanding swivel joint (made by Storm Plastics) to the pipe or else measure and cut a section from the 90mm overflow pipe then fit a 100mm x 90mm stormwater adaptor to the bottom pipe. You then slide down a short 100mm DWV pipe and connect it to the adaptor. This will then have the 90mm (outside diameter) pipe draining into a 100mm (104mm internal diameter) DWV pipe. This arrangement allows for both vertical and horizontal movement. You would also need two of the RainHarvesting Mozzie Stopper filters fitted.
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Hmmm, it seems that the Bunnings price has nearly tripled since the pandemic.

https://www.bunnings.com.au/holman-100-x-90mm-pvc-storm-socket-reducer_p4770344?msockid=3d4f1116078e6b1f2c4605bd069c6aa0

There is a new website coming but it is still a while away yet. The current website is a mess. There is a new one coming but I want to have some new products currently under final prototyping and field trials to be on the site due to the new site's holistic focus.

The Supadiverta has a website address on both outside walls. This is the same height as the internal reservoir's wall. The wall also locates the bottom of the filter, holding it in place. and the During heavy rain and when a tank is not fitted with an overflow pipe, the water will be a few cm higher than the wall as it back flushes the filter.

The plumber just needs to plumb the Supadiverta to the downpipe so the website address is level with the maximum height of water you want in the tank. The maximum height of water must not be higher than the tank's top inlet meshed basket because you don't want to create a bird bath! If it rises higher than the mesh during heavy rain when the tank is full, the water will quickly drain back to the Supadiverta when it stops raining.

The inflow rate will be minor when the water rises above the wall due to there being minimal additional head pressure when the tank is full.

It is easy to fit the pipes yourself. The siphonic outlets are at different heights to prioritise drainage to the lower outlets first. The two higher ones on the sides will merge into one pipe at the bottom and this branch can connect to either a common carrier pipe also supplied by one or more other Supadivertas or simply connect to a tank via a UV stabilised pond hose or similar. You can buy these hoses cut to your required length at various retail outlets.

The three photos below show-
1. Two linked tanks (Melbourne suburbia and a settling tank system) that are midway between two Supadivertas that service two downpipes draining approximately 40 sq m of roof each. The tanks are sitting on a chased, compacted sand base Chased bases retain the sand. They share a common horizontal subsurface pipe. No vertical risers. No overflow pipes. Extra storage capacity. No overtopping. No mesh maintenance.
2. What is seen when plumbed. A hose connects to the valve with the sprinkler adaptor to top up the pool.
3. What is unseen below ground. The hose doesn't extend to that length, I just didn't want to cut the hose for the photo.
4. Connected to an unrelated above ground tank.
5. 50mm fitting. This photo is interesting because the inlet services four Supadiverta draining equal roof areas from both sides of a garage. You can see a 40mm pipe coming through the wall, this pipes is plumbed along the garage back wall and collects the water diverted by the Supadivertas on the other side of the garage.
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