Cesspit / Rain water reuse

[Kristen]

Hi, my first post!

We moved into this house last June. I'm keen to recycle water, but retro fitting a grey-water system within the house is not viable.

So my plan is to catch the rainwater and outfall from cesspit for reuse in the garden. I would appreciate any thoughts and advice.

The current septic tank is old and knackered! so ripe for replacing. Any advice on types / brands please?

We have a 250sq.m pond, which needs topping up during the summer. Could it be a source for irrigation water?

We have total roof coverage (i.e. gutters and 5 downpipes which run to individual soak-aways) of around 400sq.m [and an additional 300sq.m with no gutter - might be able to fit a land-drain or somesuch].

The site is basically flat, with the "slope", such as it is, downhill to the septic tank location, and uphill [in opposite direction] to veg. patch.

Fitting some drainage piping to link the downpipes looks hard (digging up driveways; length of run is around 60m, and very little fall), so I'm thinking of sinking a small tank by each down-pipe (using the original pipework/soak-away for overflow) and a submersible pump with pipe to the holding area (either to the pond or a tank by the veg. patch). What sort of pipe should I use? Needs to be flexible to be easy to lay. 1" Blue MDPE pipe seems to be about 50p / m

Same from a new cesspit - small storage tank in-line in the outfall and pump to pond / storage tanks.

Our water is metered, and we average 0.5cu.m per day. Location is Suffolk, so our rainfall is modest, slightly higher during the summer months (important that we don't waste the downpour from thunderstorms therefore!) [average is 2" per month Jul-Nov and 1.5" other months] - my calculation is that 1" rain in an hour over 100sq.m, which is about the area covered by the "busiest" down-pipe, is 42L/min which even the cheapest submersible pumps can handle I think.

I would appreciate any thoughts on pipe sizes, capacity, whether my idea for pumping is daft! and anything else that occurs.

I'll keep you posted how it turns out ... so far the only thing planted in the Veg patch are Gladioli and other cut flowers - because buying them in the supermarket last year to make the house look nice cost almost as much as the metered water!

Thanks,

Kris

[LaurenGrows]

Hi Kristen and welcome to the Vine

[JennieAtkinson]

Hi Kristen and welcome. On the subject of appropriate septic tanks it woudl be worth your while contacting your local Council's Building Control/Surveyors Department (not sure what it is in England) as there may be local requirements for the type of septic tank, filters, etc that you require to use.

I'm sure there will be someone along soon to help you with the other questions!

[sewer rat]

Hi and welcome to the Vine
Lots of interesting questions!
The size of septic tank may be governed by the size of your property - specifically the number of bedrooms - but again I can only speak for nthe rules as laid down up here by SEPA (Scottish Environmental Protection Agency) who to be perfectly honest are a bunch of eejits - but a very powerful bunch of eejits.
You will need to have percolation tests done on your ground - this involves digging a large hole and two smaller holes, each a metre by a metre by a metre, then a further 12" deep square hole in the bottom. This 12" hole is filled with water and you have to time how long it takes for the water to drain away - too slow and your ground fails - and here's the rub - too fast and your ground fails !! If the ground fails the percolation test you may have to install a mound. This consists of a layer of filter sand covered with 20mm washed gravel and finally a pattern of continuous loop perforated drainage pipe sitting in 40mm washed stone. The whole thing is then covered with weed suppressing membrane and then topsoil. The mound can only be one third below ground level - hence the name ! Depending on position of mound and tank, you may need a pump to pump the effluent from the tank to the spreader pipes on top of the mound - more money !
And to top it all, you need to employ a surveyor to plan the size of mound required (surface area of the mound is important) and he / she will also be able to specify tank requirements and type.
As regards piping your rainwater, this should not be as difficult as you seem to think. You can hire a mini digger for about £50 per day. I would advise that you connect all your down pipes to a drainage chamber (five inlets , one outlet and then a 4" plastic pipe to your pond. Job Done !!
You could as you suggest have a series of tanks with pumps but seems a lot of hassle and potential problems when doing it with a mini digger and 4" osma pipe is a one off hit and problem free forever.
You say there is little fall - you can lay the pipe dead level all the way - water will always head to the outlet at your pond - so long as the outlet is above the max height of the water in your pond.
Finally, forget using the water from the cesspit / septic tank - I know it would not be allowed up here - unless you fit a high spec tank with filter pumps and even then I know SEPA would have "concerns". One possible solution may be to incorporate a reed bed filtration system, but have only fitted one and the plot was sold before we had a chance to go back and see it working properly. (You could try searching google for "Findhorn" - an ecovillage in Morayshire, Scotland - I think they recycle all their effluent this way)
Hope this helps - if you want specifics about anything, give me a shout and I'll try and help you more. Used to do this for a living - hence the forum handle of Sewer Rat !!

[Kristen]

Thanks Rat, very helpful!

Digging a trench all round the downpipes is a bit of a pain, but you make a compelling case for "pipe it and forget about it"

On the outfall from effluent treatment these guys:
http://www.biotank.co.uk/
are telling me that their output would be clean enough for irrigation. DIY install would be around £ 3,000, installation adds another £ 2,000.

I've no idea how much a cesspit for a large house - say 5 people - would cost, but given that mine needs replacing anyway, and I would be prepared to spend a fair bit extra to get all the metered water used in the house "back again" for a second use on the garden!, I'm quite keen.

Kris

[sewer rat]

Hi again
A septic tank of that size (basic - no pump / filtration system) will be between £1500 and £2000 to purchase.
Whilst I know what the manufacturers or installers claims are, and I agree with their claims having seen tests on the treated effluent, you may be wise to consult further as I know SEPA still insist that the effluent that comes out a filtration septic tank still passes through a mound, reed bed or a soakaway, and does not get pumped straight into a ditch or other watercourse which is what the tank manufacturers say you can do.
DEFRA should be able to advise - may even be sufficient info on their website.
The whole system can be quite expensive so better checking it all out first and doing it right rather than falling foul (no pun intended) and having to amend things later.
Good luck and let us know how you get on.