Patio drainage without soakaway?

[ashthekid]

Any suggestions on how is best to drain away surface rainwater from our unbuilt patio(approx 30-40 sqm) which will be the same level as our connecting kitchen/dining area and then step up to a garden grass area? We are very close to the water table and as I’m aware putting in a soakaway can be complicated by that. 

[Ferdinand]

How heavily are you re-landscaping.  

 

One option is to go for a bigger, shallower soakaway.

 

Or a bog garden, which can sometimes become a pond? 

 

Where does the water currently go?

[Gus Potter]

Can you post a sketch cross section? Try and show where you think the ground water level is.

 

Don't skimp on the detail if you want good feedback.

 

 

 

 

 

 

[Dave Jones]

feed it to where your gutters drain.

[Bonner]

Make it permeable, block paving or similar. Otherwise you will need a soak away of some sort. As a rough comparison, my garage is 45sqm which needs a 2cu.m soak away. 

[ashthekid]

Here is a rough sketch. Somebody has told me 1m3 of soakaway will suffice for the patio.

I have no way of connecting to mains/gutter drain.

 

SoakawayPlan.pdf

[Adsibob]

You need to design a 2 degree fall into your patio. The way we are doing it, is having it slope by 2 degrees from the middle of the patio to the edges, and at the edges we have brick slot drains (all along each edge) that feed into a drain which takes the water to the soakaway. There will be a pump in the soakaway which will come on once it fills to a certain level and pump the water to our sewer.

[Marvin]

and consideration of the permeability of the ground...

 

2% degree fall will work on a smooth surface but more tricky on a deep surfaced pattern.

[Temp]

Our patio sounds similar. We made it slope away fro the house to a linear drain at the foot of a wall/step up to the lawn. This goes into the same drains as the rainwater that lands on the roof. What do you do with that?

[ashthekid]

Rainwater from the roof is already going into box gutters that lead directly into the mains drain internally. there was no way to connect any pipework to the mains drain, mainly because of the distance but also it just became impossible in the end. That's why I was trying to work out what kind of size soakaway I would need but also find out if being near the water table was going to be a problem. Digging out the patio levels today so far not reach anywhere near the water table so we might be lucky. The ground conditions look really good and even the groundsman commented on how well it would naturally drain without a soakaway but i still want to be safe and cover myself. i'm paranoid about the patio flooding inside to our kitchen.

[redtop]

15 hours ago, Adsibob said:

You need to design a 2 degree fall into your patio. The way we are doing it, is having it slope by 2 degrees from the middle of the patio to the edges, and at the edges we have brick slot drains (all along each edge) that feed into a drain which takes the water to the soakaway. There will be a pump in the soakaway which will come on once it fills to a certain level and pump the water to our sewer.

Pump in a soakaway? Sounds lie the soakaway isn't big enough. 

[Adsibob]

6 hours ago, redtop said:

Pump in a soakaway? Sounds lie the soakaway isn't big enough. 

I am getting my terminology mixed up. We were originally going to do a soakaway but the BCO didn't like this because our soil is clay. So he made us pump it to the sewer. So we have an underground tank that the water from the patio runs to. Once the tank reaches a certain level the pump comes on and pumps it to the sewer. So this is not a soakaway.

[ashthekid]

That’s a pretty complicated setup just for a patio. It must be a large sized patio. 
 

For my size patio 30 sqm would a 1 cubic meter soakaway crate system suffice?

[Dave Jones]

9 hours ago, Adsibob said:

I am getting my terminology mixed up. We were originally going to do a soakaway but the BCO didn't like this because our soil is clay. So he made us pump it to the sewer. So we have an underground tank that the water from the patio runs to. Once the tank reaches a certain level the pump comes on and pumps it to the sewer. So this is not a soakaway.

 

grey water pumped chamber. As we all know soakaways are a waste of time in clay ground so it has to go somewhere else, normally the sewer although the sewer companies dont like it.

[Bramco]

8 hours ago, ashthekid said:

For my size patio 30 sqm would a 1 cubic meter soakaway crate system suffice?

 

Is there an equation for working out the size of a soakaway based on the area to be included and the permeability of the soil?

 

At what point can you realistically get BCO to agree to draining the area into the main sewer?

 

Our plans include a HUGE soakaway that will bury loads of plastic in the ground at a v large cost.   We'd love not to have to do this (or put more money in the ground, the foundations cost enough!)

 

Simon

[Ferdinand]

19 hours ago, ashthekid said:

Rainwater from the roof is already going into box gutters that lead directly into the mains drain internally. there was no way to connect any pipework to the mains drain, mainly because of the distance but also it just became impossible in the end. That's why I was trying to work out what kind of size soakaway I would need but also find out if being near the water table was going to be a problem. Digging out the patio levels today so far not reach anywhere near the water table so we might be lucky. The ground conditions look really good and even the groundsman commented on how well it would naturally drain without a soakaway but i still want to be safe and cover myself. i'm paranoid about the patio flooding inside to our kitchen.

 

How did you get that rainwater into the main drains passed them?

[ashthekid]

It was already existing so no change but the patio is new and no where near the box gutter drainage. 

[Temp]

On 01/11/2021 at 13:55, ashthekid said:

The ground conditions look really good and even the groundsman commented on how well it would naturally drain without a soakaway

 

We have some paths that just drain onto adjacent lawn. They are about 1.3m wide. House wall on one side, lawn on the other. Our soil is farmed clay. Seems ok.

 

Sizing a soakaway properly is tricky as you need a percolation test and some maths. There is a BRE guide on the subject.

 

Main issue for some is that Building Regs require soakaway to be more than 3(?) meters from house and possibly the site boundary as well.

Edited November 2, 2021 by Temp

[ashthekid]

I believe i can definitely put the soakaway 3m away from house line and 2m away from neighbouring fence.

 

[Marvin]

I understand the distance is now 5 metres from a building...

 

The regulations state that a rainwater soakaway must be located at least five metres from the wall of a building and at least two and a half metres from a boundary. This is to prevent subsidence of the wall and to stop rainwater on your property from flowing into your neighbour's garden.

 

Check out Labc soakaways.

 

M