Soak pit HELP

Bart2008 · 13-03-2008 10:56AM #1

Hi all, i need your help.

i am currently at the groundworks to my new house (Roof Stage just fininshed), have a few days off coming up and need to save money so going at the drainage myself, Here is what i know, that the rainwater goes to soakpits ( no watercourse nearby) but i cant find specifications or dimensions for these soakpits anywhere, house size is 150m2 approx.

Please help, all advise welcome?????

sydthebeat · 13-03-2008 11:08AM

http://www.webcomsystems.co.uk/soakaway_design.htm

you can download the evaluate version of this and input your dimensions.
give about 14mm for rainwater over a 50 year period

Bart2008 · 13-03-2008 12:18PM

thank you for the link but i downloaded it and couldn't figure it out at all, dont know much about rainfall and drain times etc, all i know that it is a bungalow in limerick with a normal soil content. extremely lost... i taught it was just a hole in the ground with a pipe running across it that has holes drilled in the pipe to allow the water to seap out as it runs along it.

sydthebeat · 13-03-2008 12:20PM

whats the total sq m of the roof and path to be drained?
is your drive tarmaced?

Bart2008 · 13-03-2008 12:36PM

the total area of roof and paths is 150m2 and the drive is not tarmaced.

Warrior23 · 20-06-2008 09:25AM

I'm thinking of draining the garden but since I'm living in an estate there's no where to drain it too being surrounded by other houses and footpath.

I am thinking of brining the pipes to a soak pit. Can these be located near the house? Will the ground above the soak pit be soft even if it's deep enough? Could a soak pit be located under a garden shed to hide it?

RKQ · 20-06-2008 11:39AM

The soak pit is for rain water. It should be down-hill of the house. A simple pit would consist of a 1800 x 1800 x 2100mm hole. Fill the hole will bits of brick, block etc but nothing else.

Run pipe from gutters to this hole, cover end of pipe with stone to prevent it being blocked. Cover with gadeners weed felt and cover with topsoil!

You could build more that one, but don't build close to house!

Once the lawn is done, you won't see it so theres no need to put it under a garden shed!

Warrior23 · 20-06-2008 12:20PM

Rainwater from the house runs into drains. I'm looking to drain the lawn only. Why can the pit not be close to the house?

The idea of putting it under the garden shed is that the shed area is in a good spot to run the pipes to (the shed is not there yet!), but it is right next to the house.

RKQ · 20-06-2008 01:10PM

I suppose a small soak pit could work if the ground isn't boggy. Make sure there is soakage at a depth under the lawn, otherwise the water will not soak anywhere.

Once the lawn is re-laid over the soak pit, nothing will be visible. No need to put it under a shed. If the soak pit is to be the wetest part of your garden, it would be wise to keep it away from your house and shed.

A french drain might be more appropiate to your garden. Remove sod and dig a 300 x 600mm deep trench around the perimeter of your garden. Fill trench 400mm deep with 2 inch stone, 200mm topsoil and reseed with lawn seed (no pipes required).

This solution would work depending on soil type - not too boggy! As the water could remain in the bottom of the trench, over the winter!

shakeydude · 20-06-2008 08:14PM

to size it correctly you really would need the permeability of the soil also

construct06 · 21-06-2008 12:55AM

use a t-piece at the end of your soakpit before covering with stone. that wau you have 2 outlets and unlikely both would get blocked....

No6 · 21-06-2008 11:31PM

I've just be asked for a percolation test on a surface water soakpit by a very fussy area engineer, thanks for the design link sydthebeat, but should I be doing a perc test at circa 2m depth or what, suggestions gratefully accecpted.

Supertech · 22-06-2008 10:50AM

Sorry ..... Mis read post. Didn't realise you were in an estate and draining the garden.

Supertech · 22-06-2008 11:00AM

I've just be asked for a percolation test on a surface water soakpit by a very fussy area engineer, thanks for the design link sydthebeat, but should I be doing a perc test at circa 2m depth or what, suggestions gratefully accecpted

That's the first time I've heard of that No6 - have you site characterisation done for the septic tank / percolation area on the site - the soil characteristics in the watertable trial hole should give you an idea of what the profile is like down to 2.4 metres at least.

Have you asked why they want this test? In any case, is surface water not just going to go to ground anyway? Seems a bit odd that they would look for a perc test for clean surface water

A percolation test at 2 metres is going to have all sorts of health and safety implications - seems a bit over the top to me.

RKQ · 22-06-2008 11:29AM

I agree with Supertech, seems abit over the top.

Is there a high water-table on the site?
Is the site boggy?

Can you do the percolation test yourself or are they insisting on a member of their panel? Would be expensive just to test a soak pit! (clean surface water)

Can you post more details No.6?

Seems like a strange request!

No6 · 22-06-2008 12:41PM

Yes thats what I thought but you want to meet this area engineer, insane would be a nice description, so I've just got to go with it.

I did suggest using the perc test results for the soakpit calculations and was told no its in a different part of the site.

We dont have a panel here, I do have a guy who does all my perc tests but its expensive to get another test done, so I'm considering doing it myself but I think it should be done at the base of the proposed soakpit ie 2m or so deep, the soakage rate obtained and the size of the soakpit calculated! Dare I suggest that the self same engineer dosnt really care as long as his ass is covered!! He's had a few problems with sites discharging surface water onto the roads hence this new bee in his bonnet!!

Supertech · 22-06-2008 05:49PM

Has he specified whether it's a P or a T test he wants done No6 ?
That will go a long way towards deciding what depth the holes have to be dug at.

In any case won't you get water soaking away through the side walls of the soakpit anyway? I think this guy is talking through his you know what .....

The Site Suitability Assessment Procedure is designed for treated effluent, but this would be discharged to ground through a predetermined length of perforated piping (65sq.m smallest I've ever worked with) This is obviously completey different from having a 1.8m square stone filled soakaway with water discharging into it from a number of individual points at an undetermined rate. What's he going to want - the same size for a soakpit ??

Is the site flat ? Can you move the soak to the side of the site furthest away from the road and would this sort his problem?

If the site is less than an acre, one set of test holes would have been sufficient for SR6 testing, and it would be taken from this that the ground conditions would be the same across the site. Surely he could take it as read that these results would do for surface water ?

Still think that the implications of getting into a 2metre deep hole, digging a further P test hole (or more - will he want 2 ??) and carrying out the tests are fairly onerous from a H&S point of view.

On another, slightly different note, have you considered a rainwater harvester to reduce the capacity of the soak ?

No6 · 23-06-2008 01:18AM

To my mind a P test and T test are too shallow, I need to check the BS on it ( I know there's one somewhere) but I may stand corrected, I'm not doing the soakpit for all the site, house & roads just the road leading down to the site entrance (down being the opperative word) so I wouldn't be too gone on rainwater harvesting from a road surface. I downloaded the software (evaluation version) reccomended above and will have a look at it tomorrow and hopefully arrive at a solution. I suspect if I do a T test, find a percolation rate and calculate a soakpit size based on the T test and give him something complicated that makes it look like we all know what we're doing I'll be fine (tongue firmly in cheek here!!)

slowharry · 24-06-2008 05:25PM

soak pits should be designed in accordance with BRE digest 365. basically dig bighole measure it fill with water time the drop do calcs get pit size. its a large scale p test

No6 · 25-06-2008 09:40AM

Cheers Slow harry, I've actually got that Digest, I'll have a read over it and act accordingly.:D

slowharry · 25-06-2008 10:12AM

I have attached an excell sheet i came up with on soak pit design. Its not exactly to 365 as i use met eireann rainfall data (which is location specific). its a bit cumbersome to use as exell is not my strong point so you might want to check the formulas (i.e i'm not responsible for flooding)

No6 · 25-06-2008 11:03AM

Thanks SlowHarry, I'll give it a lash.:D

Poor Uncle Tom · 26-06-2008 09:18AM

BS 6297 is also worth a read, No.6, let me know if u need a copy.

No6 · 23-09-2008 05:57PM

Just a little update (and as I need to send the software link to a friend!!) I just got the decision for the project mentioned above, did the test myself and put the calculations on a spread sheet from BRE 365 and checked against the soakpit designer software. Now all I have to do is get paid for it!!! Thanks for all the help lads.

muffler · 23-09-2008 06:03PM

No6 wrote: »

Now all I have to do is get paid for it!!! Thanks for all the help lads.

No need to thank us, just post a share of your fee when you get it.

rawat167 · 26-07-2010 01:31PM

Please tell me how to develop a soak pit and how much we need to expance on it.
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Mod edit: I have no idea why you posted that link but please dont do so again. Thanks

muffler · 26-07-2010 01:34PM

rawat167 wrote: »

Please tell me how to develop a soak pit and how much we need to expance on it.

What do you need a soak pit for?

sydthebeat · 26-07-2010 05:26PM

just a spammer i think muffler....

LazyPianist · 22-09-2010 02:56AM

When does a property require a soak pit ? I live in a housing estate, and I've been told that one should be built in the back yard - I'm building a 25 square yard extension in the back yard. But I don't see the point ? The rain water just drains into a gulley from what I can see. Why can't the rain water piping on the new extension convey rain water to the existing gulley ?

650 euro to have one installed too. Seems a bit odd.

sydthebeat · 22-09-2010 11:44AM

LazyPianist wrote: »

When does a property require a soak pit ? I live in a housing estate, and I've been told that one should be built in the back yard - I'm building a 25 square yard extension in the back yard. But I don't see the point ? The rain water just drains into a gulley from what I can see. Why can't the rain water piping on the new extension convey rain water to the existing gulley ?

650 euro to have one installed too. Seems a bit odd.

1. who told you you needed a soakpit

2. just because there are gullies doesnt mean there is necessarily a storm water sewer network.

contact your local authority, either roads or environmental section, and ask them.

It would be unusual, but not impossible, that the storm water from the development goes into soakaways. Even if there is, the addition of approx 30 sq m of roof area may not be significant

homewardbound11 · 23-09-2010 09:17PM

Hi No 6. I can forward on my soakway test that was done for my site in the same area as yiursekf - mayo. it should be on my planning number in mayococo. if it is any use to you.

Soak pit HELP

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