Sump/pump in garden to take water away from house?

[pb2012]

Hi all,

See the diagram attached for a visual explanation here.

We have an extension on the back of the house. Due to one reason and another the bifold doors that go across the back and set pretty low in the brickwork. There will be a 1 - 1.5 brick stepdown from the sill to the ground.

To the side of the extension is a manhole cover. Under there is a drain which takes waste down a run of 4 houses to the sewer. In the past this drain has been a bit overloaded when there has been a random heavy prolonged storm, which causes water to come up out of the man hole for the houses further down the run.

I'm a bit concerned about this happening and water building up in front of the bifolds, and coming in to the property.

I'm thinking about burying a sump/pump to intercept any water coming up and take it the back of the garden, as shown in the sketch. My questions around all of this are:


1) there will be an aco drain in front of the bifolds. However, if the drain gets overloaded this will be quite useless. Is it ever an option to put holes in the bottom of an aco drain to give water an alternative escape when full?

2) Can you see any issues with the sump/pump idea? I have easy access to power to plug in a pump. I was thinking of getting a container and lid, and to just plonk one of these in it:
Titan 750w >

3) in the event of a flash flood and water rising up against the bifold doors, how likely are they hold the water back without leakage? Doors are smart visofold 1000, aluminium frame.


The objective is to get water away from the doors/extension for as long as is needed, until excessively heavy downpours stop.

 

[Ian H]

Are the doors the lowest point? It would have to be some downpour to overpower a 4” drain unless there was a problem with it.

If your aco has a few pieces each one has the ability to have an outlet so you could run 3 outlets to a chamber and pump from there. But if the downpour is that bad your chamber will fill and the aco’s overflow anyway.

 

[pb2012]

Are the doors the lowest point? It would have to be some downpour to overpower a 4” drain unless there was a problem with it.

If your aco has a few pieces each one has the ability to have an outlet so you could run 3 outlets to a chamber and pump from there. But if the downpour is that bad your chamber will fill and the aco’s overflow anyway.

Yea the doors are the lowest point. I'm not concerned about any other area.

There was a succession of 3 heavy storms one after the other a couple of weeks ago. The neighbor 3 doors down had water pumping up out of their manhole and some went in their kitchen. They are at the end of the drain run though, and only have a non-weather timber door as defense. Their door also sits low.

Connecting the sump chamber to the aco's is a great idea! I could easily do that. The pump will be automatic with a float and kick in if ever needed, pumping to a bed at the back of the garden. This would hopefully be a once a year event.

FYI the drain is a run across 4 old victorian houses, and the sewer network does struggle under unprecedented downpour.

 

[pb2012]

Any idea how well a set of properly fitted bifolds are likely to hold back a few inches of water in a quick flash flood situation?

 

[pilsbury]

So your doors are 1.5 bricks up? Is there a possibility of 4" water on your patio or whatever you have out back? Is your garden sloping towards the house?

 

[pb2012]

So your doors are 1.5 bricks up? Is there a possibility of 4" water on your patio or whatever you have out back? Is your garden sloping towards the house?

Not sure about possible water height. I do know the neighbor further down the run has had issues. They are the end of the drain run though, and I'm the start of it.

At the back will just be earth, no hard standing. We intend to deck over this as it seems a more sensible option from a drainage point of view.

The garden has a slight slope towards the house at the moment, but I'd like to flatten it, or even slope it away. Not sure how many skips worth of soil that will involve...

 

[Footsoldier888]

I think you need to be careful about this because if you haven't got Building Control sign off for this drainage system there is a good chance you would be liable for repairs to the other properties if they have suffered damage as it seems you are discharging rain water onto their land. It seems surprising the water company haven't been called out and traced it back to you seeing as the drain is theirs, it being a lateral drain.

Perhaps you need to go for a SUDS solution in order to control the discharge of this water, like a holding tank that releases slowly.

 

[^woody^]

Bonkers.

How big a pump do you think you will need for this random deluge of unknown amount for indeterminate period of time, for unspecified quantity of water on the patio area?

And where is the pumped water to go in the unknown storm when it's lashing down on every bit of ground and the ground is saturated?

Might be better to get the drains cleaned.

 

[rssteve]

I've got the same doors at home. Which threshold did you go for as I seem to remember the flush threshold is not rated for external use although plenty of people use it without issue. Mines about 15mm and gets the wind of the South coast and although the water does get in the frame it drains out the bottom. There's no way it would hold water back if it rose above the threshold though.

 

[pb2012]

Bonkers.

How big a pump do you think you will need for this random deluge of unknown amount for indeterminate period of time, for unspecified quantity of water on the patio area?

And where is the pumped water to go in the unknown storm when it's lashing down on every bit of ground and the ground is saturated?

Might be better to get the drains cleaned.

Bonkers because you think it is all unnecessary, or because it wouldn't work? Or both?

I figured that pumping the water right to the back of the garden until a heavy downpour weakens off would stop it having a chance of rising up against the doors.

 

[pb2012]

I've got the same doors at home. Which threshold did you go for as I seem to remember the flush threshold is not rated for external use although plenty of people use it without issue. Mines about 15mm and gets the wind of the South coast and although the water does get in the frame it drains out the bottom. There's no way it would hold water back if it rose above the threshold though.

Heyup, thanks for the info.

15mm is pretty small, that's almost flush? Is it classed as the 'low' threshold?

Mine will be the 50mm rebated threshold (weather rated) with 25mm sill under it. 75mm in total, sat one and a bit of a brick up from ground level. This kind of thing >

Does your 15mm threshold have a rebate and a seal that the door jams back against? I'm guessing it's this one > (with brushes rather than a rebate/rubber seal)?

 

[^woody^]

Bonkers because you think it is all unnecessary, or because it wouldn't work? Or both?

I figured that pumping the water right to the back of the garden until a heavy downpour weakens off would stop it having a chance of rising up against the doors.

Both.

The amount of water that would go down a drain to cause it to surcharge and flood your property three houses up would require a pump probably as big as your extension. And then, the water you pump elsewhere would flood that place too.