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Slot Drain Problem

4K views 5 replies 3 participants last post by  keredwh 
#1 ·
I've got a concrete slot drain in front of the garage which appears to have a 100mm outlet at one end.

My problem is that when it's raining, even though there is little water running into the slot drain itself, I can see water rising up from the outlet sufficient sometimes to fill the drainage channel, overflow and flood the garage!

The water will drain away slowly over a few hours.

Curiously, if I put a hose pipe down the drain and turn the tap on full, no water backs up and the drain clears fine.

There are no signs of any inspection chambers on the property and no obvious connections to any neighbours drains. It is possible that one or more gutter downpipes connects somewhere but it's not obvious where and I doubt if there is enough water coming from the roof to cause this problem.

I can get access to the outlet and have had a contractor round to look at it but he seemed reluctant to rod the outlet just to see what would happen. I can't think why and was wondering if it would be wise to have a go myself.

Anyone got any ideas what is happening?
 
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#2 · (Edited)
1. The water is obviously coming from somewhere and your contractor should know what feeds into this drain. He can tell you. You are probably right about it being from gutter drains. You would be surprised at how much water comes off a roof.

2.Water always flows downhill. So the contractor may have sloped the drainpipe to flow to the slot drain instead of away from it.

3. If a drain pipe isn't big enough to handle the water volume, then the water just takes the alternate lowest path (your garage). So maybe the drain pipe isn't big enough - especially if gutters are also draining into it.

4. Your hose can't put out as much water as a rain.

5. The contractor who installed it is responsible for fixing this (assuming this is a recent install). It's not acceptable.
 
#3 ·
Is this an attached house situation? Is the garage at ground level or below? If you put the hose into the place where the leaders enter the ground, do you see water in the garage drain? Do you hear water flowing at the garage drain? What material is the pipe made from? Do the drains empty into a drywell? Street? Some garage drains are just holes in the ground where the water can, but not always drain. If this is the case, ground water can also rise up out of the hole depending on where it is relative to the surrounding area.
There are guys who can snake a camera through the drains to check for problems. They're not cheap.
Ron
 
#4 ·
Thanks guys! Really helpful.

jogr, the house is just outside the NHBC warranty (we bought it just after it expired last year!!) and the builders have flatly refused to provide any drawings saying it is against their policy! Consequently, I have no idea where it drains to. Favourite theory is that it heads back under the slot drain, effectively doubling back on itself and heads towards a storm drain running up the side of the house beneath the road but there is no way of telling.

We're built on a hill and by no means the lowest house on it.

Ron6519 the pipe is plastic as far as I can tell. The drainage contractor I contacted was reluctant to put a camera down there which surprised me.

I'm going to try rodding it and see what happens but I may be left with no alternative but to rip it all up and see what is happening!

Any other thoughts are very welcome.
 
#5 ·
They may not actually have drawings of the drain system. But in some areas they may have filed drawings with the local building department to get the permit.

Try getting info from your local building department. If that's not successful, then revisit the builder. Make sure he understands that all you're wanting is some information. If the builder won't cooperate with info then let him know that he's forcing you to become more public with the problem.

Did it not rain when the previous owner lived there? They should have disclosed the defect.
 
#6 ·
jogr I have spoken to the local authority who advised me that the building control on this estate was done by NHBC and as such they are the only people who may have a drawing.

The NHBC have told me they MAY have a drawing but cannot release it without permission from the builders for copyright reasons. The builders are refusing permission as well as refusing to let me have their copy.

I've considerd going public with the details but want to keep that as a last resort option.

My wife tells me that when we first visted the house, it was pouring with rain and there were no signs of problems. Personally I can't remember if it was raining or not but I would definately have remembered 2" of water in the garage and having to wade to the front door!

The other odd thing is that it is intermittant. Sometimes it will pour down and we will have no flooding at all! It's darn infuriating!
 
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