Mum's rainwater setup help?

[guydewdney]

My mum is building a fair size house - and part of the building regs demands  that there is a RWH system for watering plants.

I have scabbed two ekking gert tanks - totalling 5,000 litres. There is a JCB ready to dig a gert hole to chuck them in.

I was going to KISS - pipe that usually goes to soakaway will have a short, perforated, section in it- this section then goes to the tank(s) below the pipe. Second tank has breather pipe to allow air out. Join tanks at bottom.

awful scribble below. Not to scale! Filter section should allow leaves to be washed along pipe to soak away (SA). Sump pump dropped in to provide water for garden.

[Iain]

Hi
The filter/pipe will probably let the small sediment into the tanks. Could a different filter be better?
How about having a take off for toilet flushing,etc. 5000 lts might also be a bit small. I store up to 6000 and nearly ran out. If you are digging a hole for 2 tanks I would probably go for at least 3 tanks.
Nice to see on new build, it is often easier than retrofit.
Iain

[solar_cambridge]

I have no idea what a 'ekking gert tank' is but anyway! I realise your drawing isn't to scale, but tanks just need to be under the surface, so I don't think you need a breather tube. Also don't join the tanks underground as its a point of leakage. How about a twin impellor pump so that one side feeds the outlets and the other side pumps from the second to the main tank. Secondhand they are cheap enough.

Is there one single downpipe or several to connect. Look at the plumbing issue with the downpipes and it might be easier to have decent inline filters. I tried two of the '3p' filters from rainwaterharvesting.co.uk and found them to be excellent and cheap enough to have on different downpipes rather than try to redirect big ugly downpipes!

[dhaslam]

I saw on a TV program  several years ago a gadget that  disposed of the first  pint or so of water  from the roof.    When it filled up  it tipped over, spilled the dirt and silt from the first flush of water  and subsequently all  the water went into the tank.    I haven't  seen any reference to one since but I suppose it would be easy enough to re-invent.      Pretty bad year for collecting water so far, it would be nice to have a few  big tanks full.

[guydewdney]

I don't know the exact details of the pipework yet - but I suspect that it would be easy enough to join them all together underground (the roof is a wide V shape).

I was going to bury them just a foot underground - hence the breather.

Ekkin gert means large oil tank, new, from Deso (a local rotational moulding company) - these are rejects for visual reasons.

Two pumps Vs 1 pump and a balance pipe? Not sure which is more 'reliable' - why should a thick galv steel pipe leak in the forseeable future?

Filter - yes - I am not overly happy with the suggestion - thanks for the link - http://www.rainwaterharvesting.co.uk/proddetail.php?prod=RWH-CF1 is what I was inventing in my mind! seems a bit steep for a T piece with a bit of mesh...

[knighty]

as they're underground anyway, why not stick one tank (the one with the pump in it) a bit deeper than the other ? (doesn't need to be much)

and that way you'll only need one pump, and you should be able to drain both tanks practically dry if needed ?

[tony.]

if your using steel pipe underground i personally recommend the most evil substance known to man- denso tape, wrap it around the flanges/joining pieces  etc

tony

[guydewdney]

1 roll of sticky goo to be ordered...