Green Building Forum - No Mains Drains - what do I do?

No Mains Drains - what do I do?

Katymac — Fri, 09 May 2008 20:32:01 +0100

I have been told a water treatment plant - I don't really know what that is, could anyone elaborate?

Also would to cost of collecting & storing rain water or waste water to flush five toilets be practical? - baring in mind I would have to dig soak-aways if I don't re-use it

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No Mains Drains - what do I do?

tony — Fri, 09 May 2008 22:15:50 +0100

Me too. Anything that treats the water is a water treatment plant -- simplest might be a reed bed a small version of the one they use in Cairo would do you.

Or a digester or something more expensive.

Think about having a dry composting system too -- you may even be able to sell the compost!

Yes you could collect rain water for the flush if you need them.

No Mains Drains - what do I do?

ted — Fri, 09 May 2008 23:43:38 +0100

They are most likely thinking of something like a Klargester or Acorn:

http://www.ohel.co.uk/products/biodisc_ba-bax-bb.html?gclid=CJumxra8mpMCFQyD1Qodsm91ng
http://www.acornsystems.com/

You would need to get one of the correct size and also pay attention to servicing and de-sludging frequency as well as the energy input required.

No Mains Drains - what do I do?

Neil K — Sat, 10 May 2008 08:01:26 +0100

We have just had permeability tests done that failed, so the planned septic tank & soakaway option is now out. The guidance notes recommend either a drainage mound or a bio-disc such as the Klargester etc.

The problem seems to me that whilst a Klargester or similar is easy to install you are then committed to 50W of power use for the life of the property! (438kWh/year!)

I am trying to find information on the sizing of the alternative of a drainage mound. The information seems very sketchy on the design, so glad of any experience or pointers.

For background: there is an adjacent ditch, the site is agricultural land comprising boulder clay over impervious sandstone and we have enough space for a mound.

No Mains Drains - what do I do?

Katymac — Sat, 10 May 2008 08:09:43 +0100

Sizing looks difficult
30 children - 10 of whom will be in nappies (n average)
6 staff
Washing machine & dishwasher
No shower or bath

That won't be easy to work out

No Mains Drains - what do I do?

richardt — Sat, 10 May 2008 12:03:27 +0100

Neil,

We're also on clay, original LA preference was for mounded soakaway, we convinced them that 2-stage reedbed & pond would work better. Also more pleasing to the eye and to the wildlife. You'd need a bit more land though.

No Mains Drains - what do I do?

CWatters — Sat, 10 May 2008 20:42:48 +0100

Katymac - has the existing nursery got a water meter? Check water consumption as that will roughly equal the waste you have to dispose of. Plus rainwater if you don't harvest it.

No Mains Drains - what do I do?

Katymac — Sat, 10 May 2008 21:06:27 +0100

Existing Nursery? don't have one of them

No Mains Drains - what do I do?

joe.e — Sat, 10 May 2008 23:47:44 +0100

Katymac, how much land is there available?

No Mains Drains - what do I do?

Katymac — Sun, 11 May 2008 09:24:33 +0100

17m by 6m

No Mains Drains - what do I do?

Neil K — Sun, 11 May 2008 17:33:25 +0100

Richardt,

Thanks for the information on the reed bed option.... I have been looking into this and think we may head this way. How did you get it sized by the way? We have the space, but glad for any anecdotes,

Neil

No Mains Drains - what do I do?

richy — Sun, 11 May 2008 19:27:42 +0100

Doesn't sound like much room for a septic tank. The outflow usually covers that sort of area. What's the situation with building regs and composting toilets everyone?

No Mains Drains - what do I do?

Katymac — Sun, 11 May 2008 20:55:15 +0100

Oh dear - that sounds bad

No Mains Drains - what do I do?

ted — Sun, 11 May 2008 21:18:38 +0100

The output from the mini treatment plants is 'clean' water so you just need a place for this to go to. Needs to be at least 10 meters away from a watercourse if I remember correctly otherwise you'll need a consent from the Environment Agency.

No Mains Drains - what do I do?

Katymac — Sun, 11 May 2008 21:26:32 +0100

Can I flush the toilets with it?

Will grey water & rainwater recycling help this or not?

Umm I'm about 1/4 mile from a river

No Mains Drains - what do I do?

nigel — Sun, 11 May 2008 22:49:36 +0100

There is a minimum distance for one of these units from a dwelling which I think is 15 metres.

You should check this with your BCO.

No Mains Drains - what do I do?

Katymac — Mon, 12 May 2008 08:00:22 +0100

That's next door

No Mains Drains - what do I do?

CWatters — Mon, 12 May 2008 08:28:05 +0100

What are you building that needs to accomadate the following if it's not a day care nursery? Perhaps go find another similar place and ask them about their water consumption.

30 children - 10 of whom will be in nappies (n average)
6 staff
Washing machine & dishwasher
No shower or bath

No Mains Drains - what do I do?

Katymac — Mon, 12 May 2008 08:47:38 +0100

Mine will be day-care - I just don't have access to an existing one (iyswim)

I think I will have to do some careful research

No Mains Drains - what do I do?

richardt — Mon, 12 May 2008 12:30:42 +0100

Neil,

We got the calcs done by a boffin from the Scot. Ag. College as a bit of heavyweight credibility and proper scaled drawings were required. He basically confirmed what I'd already worked out from a CAT pamphlet. Lots of farms here at least are putting them in downstream from cattle courts &c so finding competent groundworks contractors is getting easier.

No Mains Drains - what do I do?

Katymac — Wed, 14 May 2008 08:57:47 +0100

If I have a water treatment plant or a septic tank will the water coming out of either would be good enough to flush the toilet with?

If I recycle rainwater & flush the toilet with this water will I still need soakaways?

No Mains Drains - what do I do?

CWatters — Wed, 14 May 2008 09:36:11 +0100

To answer the last question...

If you size your rainwater store correctly you may not need large soakaways but you are likely to need some provision in case collection exceeds demand (eg when the day care center is closed for holidays etc). The BRE have a guide on constructing soakaways. If I remember correctly it has information in it on calculating the amount of rainwater your roof is likely to collect.

The collecting tank needs to have normally empty buffer space so to cope with thunderstorms.

In some countries they discharge rainwater onto the ground around the house rather than collect it... I know it's a waste but perhaps check out this for outbuildings etc

http://www.rainbreakerz.com/customer/home.php

No Mains Drains - what do I do?

ted — Wed, 14 May 2008 16:48:06 +0100

You'll need soakaways as it would be impractical/costly to size the rainwater tanks to be large enough never to overflow.

The calculation is pretty simple:

for every 1mm of rainfall each square meter of roof collects 1 liter of rainwater.

So if your average annual rainfall is, say, 1200mm and you have 30m2 of roof area to collect from then you have:

1200 x 30 = 36,000 liters of potential water to collect each year.

If a thunderstorm dumps 50mm of rain in one hour on the same size roof you will have:

50 x 30 = 1500 liters to handle. That's a lot of water and if this happens when your tanks are already full then it will all have to overflow to a soakaway.

The Met Office website has details of average rainfall for different parts of the UK with monthly figures too.

You'll probably need to decide how many days without rain you can afford to size the tank to support you through, although cost will be a factor that will require you to compromise and switch to mains water to cover short periods of drought.

No Mains Drains - what do I do?

Katymac — Wed, 14 May 2008 17:31:07 +0100

Thanks Ted

Building control were out this morning and they suggested no soakaway and to use the outlet water from a water treatment plant back into the rainwater recycling tank - I was a bit mind blown by this and need to think about what you said about cost carefully

No Mains Drains - what do I do?

ted — Wed, 14 May 2008 18:09:28 +0100

You might find that what they suggest is a little impractical.

The outlet from a treatment plant will be at least 750mm below ground level. To get this to gravity feed into the rainwater tank will mean having an inlet lower than this (how far below depends on how far apart the two will be). This means a deeper hole than otherwise required for the rainwater tank plus, maybe, concrete rings for manhole access, etc.

You can get pumped outlet treatment plants, so you're not relying on gravity, but they cost more to buy and to run - consuming electricity which isn't what we want.

No Mains Drains - what do I do?

Katymac — Wed, 14 May 2008 19:28:39 +0100

doncha love professionals..........

OK more stuff to think about - at least when I talk to companies I will have an idea of what we are talking about