Percolation tests

[Feltwell]

Now I've got the planning permission for a new garage, time to put in for Building regs...

My house is served by a combined sewer, i.e. drainage from the roof and foul water from the house go down the same pipe. Building regs now apparently insist on any new extension using a soakaway for its rainwater drainage, rather than using the existing sewer connection, so long as the soakaway will function OK.

Googling "Percolation tests" brings up lots of links for tests for septic tank discharge, but little for rainwater discharge. Anyone know a good source for the test method, how to calculate the results and the pass/fail criteria?

I suspect mine will fail, as the water table is quite high. The garden is about the same level as the cellar floor (the house being on a slight hill) and the cellar has flooded during the winter.

 

[Penners]

I can't remember how large your garage will be, but I think I'm right in saying that if it's under 30m^2 floor area (internally), you don't need building regs consent.

I can't vouch for whether that waiver includes surface water disposal, but the article I read didn't mention this as an exception to the waiver.

 

[JoceAndChris]

A nice thicket of bamboo, preferably with attached pet panda, should sort out any soggy ground issues.

 

[Feltwell]

Alas, the boys toys to go in said garage need more than 30m2, so I have to comply with the regs.

A nice thicket of bamboo, preferably with attached pet panda, should sort out any soggy ground issues.

That's what I like, practical thinking! I shall call Whipsnade first thing in the morning! "Got any spare Pandas Guv?"

I'd be perfectly happy for a soakaway not to be an option - don't particularly want a whacking great hole digging in the middle of the garden, and there is a sewer connection right next to the garage which I need to connect to anyway as I want to put a sink in the garage. Oops, that's not very green of me is it?

 

[JoceAndChris]

Sorry to thrust another green idea your way, but is guttering around your garage, all leading into a water butt, not an easy solution? It requires a lot of tiresome swooshing out of leaves, but don't worry, I can send along some giant millipedes if this all gets too much...

Or is it so wet in Shropshire you don't bother watering your garden and have no need of a butt?

 

[biffvernon]

I can send along some giant millipedes

Good to hear you've been feeding them well.

We live on a beach, or at least it was a beach a few thousand years ago, and the sand, gravel and sea shells allow water to drop straight through.

 

[Feltwell]

Sorry to thrust another green idea your way, but is guttering around your garage, all leading into a water butt, not an easy solution? It requires a lot of tiresome swooshing out of leaves, but don't worry, I can send along some giant millipedes if this all gets too much...

Or is it so wet in Shropshire you don't bother watering your garden and have no need of a butt?

Well, we're pretty close to Wales, and it would be selfish of the Welsh to keep all the rain!

Too much roof to just rely on a water butt. I could fit one - probably won't bother though as I want to get the old pump at the end of the garden working to give water for the garden, as we have a well we may as well use it. The garage does need to have a proper drainage arrangement, it's more just querying if anyone knows where the correct calcs can be obtained from for a percolation test so I can tell building control.

 

[MdB]

... it's more just querying if anyone knows where the correct calcs can be obtained from for a percolation test so I can tell building control.

http://www.planningportal.gov.uk/england/professionals/en/4000000000382.html

Read Section H3. In particular, 3.23 to 3.30. Section 3.28 refers you back to section 1.34 of H2 which gives you the test method.

You did ask....

 

[Wren]

I think it is on the environment agency website somewhere.
Dig a hole of a certain dimension, fill with water and let drain away, and then do three test runs each time pouring in water and then timing how long it takes to drain away.
We tried doing this ourselves in an area where I thought we might be able to put a drainage field (for various reasons need to replace current cess pool). But it was very depressing - the first lot of water (ie before the ones where you start to time it) didn't drain away it just stayed there. So we are left with the option of pumping it uphill (to where the soil is less clay-ey) which doesn't seem to make alot of sense, or dunno.

If you suddenly decide to get interested in the whole subject of rainwater management you could look up the following book. I happened to be in bookshop shortly after the dramatic floods which occurred across various parts of England in Summer 2007 when I spotted it, and couldn't resist flicking through it. Not sure to what extent the sort of solutions the book proposes would have helped in the event of such extreme rainfall conditions - very significant? or just a drop in the ocean, oh dear bad pun must stop now.
Rain Gardens: Managing Water Sustainably in the Garden and Designed Landscape: Sustainable Rainwater Management for the Garden and Designed Landscape by Nigel Dunnett (Author), Andy Clayden (Author)

 

[Feltwell]

http://www.planningportal.gov.uk/england/professionals/en/4000000000382.html

Read Section H3. In particular, 3.23 to 3.30. Section 3.28 refers you back to section 1.34 of H2 which gives you the test method.

You did ask....

I did indeed - thank you for that, that is exactly what I was after. 69 pages on drainage systems should also cure my insomnia nicely!

Thanks also Wren. I could find lots of stuff on septic tank soakaways on the web, but not rainwater soakaways. Your problem sounds rather depressing - hope you get it sorted.

 

[DaveBrigg]

If this is clean rainwater, can't it be piped into the old well (providing, of course, that the well is accessible).

 

[Feltwell]

Nice idea, but unfortunately the well is too far away from the garage for that to be economic. It's also a bit of a grey area as to if the land it is on belongs to me or my neighbour.

 

[CHRIS]

Our old friend here is a good place to start

http://www.pavingexpert.com/drain08.html

This should be most peoples first port of call with regards to paving and drainage - especially DIYers