How close together can rainwater soakaways be?

[phatboy]

Hi,

We are extending soon, and need to drain (Including the existing house), approx. 150sqm of roof area. Without knowing enough, I decided that 1 engineered soakaway would be less hassle than 3x 1m2 ones dotted around the garden.

Having now been advised the size of the test pit (With no digger access until we start demolition), and the volume of water required to conduct the test, I am wondering if we can just use 3 small ones.

I keep finding that they must be 5m from the house, and 2.5m from boundaries. But how far apart from each other would they need to be?

Soil is sand, the area used to be sand dunes.

Any help much appreciated.

 

[phatboy]

I feel like I ask all the difficult questions!

 

[^woody^]

Why cant the existing house use the existing drainage - unless that's a soakaway?

Soakaways don't need to be 5m from a house nor 2.5m from a boundary, and certainly not 5m from each other.

 

[phatboy]

Why cant the existing house use the existing drainage - unless that's a soakaway?

Soakaways don't need to be 5m from a house nor 2.5m from a boundary, and certainly not 5m from each other.

Thanks for the reply. The existing house drains into the sewers, an alteration made sometime a long time ago before we were here. As a compromise for some other bits we wanted, we agreed to correct this issue.

I understood that they needed to be 5m from the house, 2.5m form the boundary (Typo above now corrected), unless an engineered solution was used? Which is what I'd like to avoid due to the challenges and costs of getting water tankered in.

 

[^woody^]

If it's not technically or practically possible to correct the issue, then you should not have to do it.

However, according to the BS and BRE guides (on which the building regulations are based), there is only mention of the potential impact on foundations - and even then it is stated as "not normally" and not "not ever".

Subject to suitable design, design capacity and local ground conditions, a soakaway could go much nearer to a house. Likewise a boundary.

 

[phatboy]

Thing is it is possible, especially as the extension will cover the existing drain run, and it will be removed regardless as its pitch fibre. It's going to the foul drain, as we don't have a storm sewer in the road that we can use.

I had understood that anyone could design a soakaway where it was 5m from the house and 2.5m from a boundary without any further considerations, but when they got larger, or closer, then engineers needed to have calcs for it/them?

Subject to suitable design, design capacity and local ground conditions, a soakaway could go much nearer to a house. Likewise a boundary.

This is the bit I'd like to avoid, or at least have an idea of what's allowable before going back to the engineer - discussions cost money