Thread: Advise on plumbing downpipes to drinking water tank

I'm not a plumber or a builder so don't really know. All of my pipes are 100mm white shiny plastic pipes with no diverters etc and the joints are all glued with some blue stuff.

But, I would make sure that where the water flows into the tank that you have a flyscreen mesh over the tank so that all of the roof gunge gets filtered out. I clean mine out every day that it rains and I don't have any trees around the house - its just mud, bugs, algae, I've had a bird etc etc etc filtered out from it and there doesn't appear to be any visible dirt on the tank floor under it. Also, make sure the tank outlet also has a fly mesh to stop birds, animals etc from getting into the tank also.

The 100mm is fine to collect roof water and go underground for tanks. The main issue with going underground is that you will have standing water in your pipes between rain falls. This is not normally a major issue and what you are thinking of doing is quite a common and acceptable solution.

All joins should be cleaned, prep'd (the red stuff) and glued. The standard PVC glue is fine, but if you have any joins visable, use the clear glue and not the normal blue stuff. (cosmetics only).

Check with a local plumber about pipe depths. Water diverters are a interesting topic as most common ones will not hold enough water to achieved a clean roof before they re-direct to your tanks anyway. The ball float/T piece type usually only has a couple of metres of PVC for "first water" collection and this does not even come close to the amount of water the average house roof collects in the first few minutes.

Make sure your tank inlet and outlets are screened.

Fit leaf traps at a user friendly height and they will get checked regularly. If they are fitted where you need a ladder to check and clean them, it probabley won't happen as often as it should.

Take pics of your open trenches (with pipe laid) with some reference points so if you ever have hassles later you know where to start digging

HTH

If your downpipes are 100mm, depending on how many of them you are going to join together into a single line to the tank, you may have to go a bit larger. But if it's a separate line from each downpipe to the tank, then 100mm all the way will do.

Standard white PVC is OK for drinking water - I've just done the back half of my place and the shed, and plumbed them all into a new tank. PVC glue is available from Bunnings or any hardware store - but get the PVC primer as well and prime the joints before applying the glue. Gives a better joint that's less likely to leak later, and that's important especially if you're going underground.

500mm below ground should be plenty of cover to drive over - we only bury water pipes 250 - 300 below ground at work, and drive over it with 992 loaders etc. The trick is to lay a bed of sand in the bottom of your trench before laying the pipe, and then cover the pipe with sand before back-filling the trench - this protects against any coarse / sharp rock pushing into the pipe.

Originally Posted by pop058

.................. Water diverters are a interesting topic as most common ones will not hold enough water to achieved a clean roof before they re-direct to your tanks anyway. The ball float/T piece type usually only has a couple of metres of PVC for "first water" collection and this does not even come close to the amount of water the average house roof collects in the first few minutes.
.............................

Agreed

When you do the calcs,

• Each meter of 100mm ID pipe will hold a mere 7.85 litres of water.
• Each sq.m. of roof area will yield one litre of runoff for each mm of rainfall.
• Now for anywhere near an effective 'first flush' diversion you would be needing at least the initial 5mm of rainfall diverted.
• Therefore, for a small 10sq (30sq.m.) house you would need to divert the first 150 litres of runoff - which, if held in a 100mm pipe would require a length of 19.2m.

ALternatively, you divert the 'first flush' to waste or a tank used for purposes other than drinking. Which means that you'd need a somewhat more sofisticated diversion sensing system.

most down pipe is 90mm unless changed or organised with builder or plumber or unless it is a large roof with alot of water coming off it,,but not uncommon to be 100mm with all the new regs with water run off to be used as drinking or green water,for drinking water i would cut in leaf and dirt filters about head height so can be cleaned out quite often,there is alot of dirt and scum that comes off a roof with each down pour,,,most pipes when im plumbing and have to have to be inspected will be 350mm under or deeper but if no inspetion is required it wont matter if they are only a couple hundred deep,,

Only thing I would add to above is that if you have a water trap (effectively) you should ensure that it really is insect screened both from the roof and the tank (unless it is sealed into the tank) otherwise you will breed mosquitoes in it. It is also useful, in case of trouble, to have an inspection opening at the foot of the pipe up to the tank, and there is also a good case for another one just above the ground on the downpipe - so that in the unlikely case of a blockage you can let the water out there instead of overflowing gutters.

John

thanks for all the info, i had forgotten about mozzie screens.

The house roof is approx 310m2 excluding pitch of the roof which i would think will add a little bit? There are 9 downpipes fitted.
I was thinking later to plumb in the pargola downpipes too when we get one.

My plan, such as it is, (just made it up now) was to run separate pipes down each side of the house, more or less, and run them both to the tank. so in effect halving the water flow.

re: the first rain diverter I thought it was just a case of having a T piece type tap near the tank leading to waste, then after the first good down pour of the year some how switching it to the tank?

does anyone know if its OK to do this stuff yourself of do I need a licensed plumber for waste/drinking water?

So can i get all this stuff from bunnings?

one more thing is the fall from the house to the tank I assume that as long as the height of the gutter is greater than the height of the tank then all should be good?
Not sure if I need specific angles per X amount of meters of pipe so the water runs OK?

Never been on just tank water before so not sure whats "good practice

Hi
this idea comes from Rob Gray's website and is for a motor home, but the flush idea is good.



Read more about it here in the February 1 entry

cheers