Water in cellar - advice needed

[Dean B]

Hi,

This is my first post on this great forum.

I live in the larger part of a house built 1650, with an 1800 major overhaul. My half of the house has all the cellars. I've been here 3 months, and during heavy rain (and once during a light but prolonged shower) the cellar floods to a depth of about 2 inches in a puddle about 2 metres across. The water seems to seep from the bottom of the front wall in two or three places (not continuous along the full width of the wall) running down into the lowest point of the floor. The walls are sandstone with rubble infill. The water doesn't seem to be rising up the wall more than an inch or so. Original flags abutt this sandstone wall. The sandstone in the bottom course is still stable despite this water ingress. The house lies on a hill, and the flooded area is the downhill side of the cellar. The cellar floor is about 7 feet below ground level on the dry side and 4 feet below ground level on the side where the water seeps in. A neighbour further downhill (on the other side of the road) has a cellar which she claims has never flooded.

I've done some research on the internet and initially put it down to increased water table levels flowing down the hill underground, and I was planning to build a sump in the floor to deal with these occasional rises. However the last 2 or 3 times the water has really smelled bad so I called Wessex Water last week and they sent a crew out. They checked all the drains around the house and the sewer in the road for blockages and it was all flowing freely (however the rain had stopped by the time they came). They tested the water in the cellar and confimed it was foul although it was not too strong and they suggested it could just be groundwater contaminated with decayed leaves rising up during heavy downpours.

After reading a few webpages on water tables, I think now that it cannot be groundwater as groundwater rising naturally should be fairly clean and it smells too bad to be anything other than sewer related. The chemical test done by the Wessex Water chap identified amonia contamination. I'm no expert on how sewers are constructed, but I had a good look when the water guys came out and I'm sure that there is only one system for rain and foul in the road. My guess now is that when it rains heavily the drains overflow and foul-contaminated water is discharged into the surrounding ground. My cellar wall is about 7 metres from the main drain in the road and the land between my house and the road is flat. The hill continues down from the otherside of the road.
There is no domestic drain in the vicinity of the cellar (my drain goes into next door's garden and joins the main about 15 metres down the road).

The guys from Wessex Water were looking for the obvious (a blockage) and when they couldn't find anything they left scratching their heads saying there was nothing else they could do. I obviously don't want contaminated water in my cellar (even if it were to be contained in a sump and pumped back out again).

Has anyone else encountered anything similar, and if so what was the cause and how was it resolved? Is my theory about the main drain overflowing plausible (there is no evidence above ground that it overflows)? If it is the main drain, is Wessex Water liable for rectification costs, even though the problem seems only to appear in my cellar?

Any help or advice will be gratefully received.

Cheers


Dean

 

[Johneds]

If the water is coming from the main sewer then it is a sewer leak/overlow and it matters not that it is occuring below ground. It is just the same as if the overflow was occuring at ground level and the foul water was spilling into your living room?

So it is really just a question of establishing the facts. Firstly, don't take everything Wessex Water say on face value. I have just come to the end of a twelve month battle with Wessex who denied responsibility for a public sewer because it was 10 metres below a main arterial road and was going to cost £75k to repair. It was a public sewer and the repair has been completed in the last 5 weeks at huge expense - to Wessex Water!

The main problem is that proving the problem is with the sewer will not be easy and may be expensive. And of course it might turn out that it is not the sewer at all.

The simplest method is to hire a ground drill and take some samples closer to the main sewer. If the problem is with the sewer then the concentration of foul smell should increase as you get closer. It obviously depends on your ground conditions but drilling down 7 or 8 feet is not normally too much of a problem. Of course you need to avoid other services - so hire a commercial cable/pipe detector as well.

 

[Lime]

Without going into other detail, I think the first thing I would is is this, next time it rains heavily take up a manhole cover or two and see if the main sewer is backing-up.
The sewer may be free flowing but it may not be able to take the volume of the storm flood water.
If it is backing up then every sewer pipe in and around your house is filled with sewage and able to seep out of any crack. Some cracks in old pipe can leak for decades causing large fissures running through the ground. Your cellar may be the nearest lowest place for it to run.

 

[worms]

Dean,

I have no experience with water companies or wet basements, but it is quite easy for any reasonably equipped laboratory to determine whether water is grossly contaminated with faeces rather than dead leaves. You want to get someone to do a water quality check for levels of faecal coliforms. I would ask the water company to do this to prove that the water isn't from the sewer and if they refused, I would go to the Council's trading standards and see if they can help - they would have labs that they use to check for coliforms in private water supplies. If it is sewage seep the level of faecal coliforms will be high, if it is from vegetable decay they will be much lower.

 

[Lynn]

it could just be groundwater contaminated with decayed leaves rising up during heavy downpours.

Say what? Decayed leaves in groundwater?

I think lime has it right. If it is sanitary and storm sewer that is combined (which is a very bad idea) or if the sanitary sewer is getting groundwater inflow because it is old and full of holes, then you may be at a low point where the pipe gets enough head to leak and finds its way to your cellar.

I'd check a manhole during the next big rain and if the pipe is full then there could be enough pressure to shoot it your way...bad luck if it is so.

 

[Geoff Flegg]

I'm sure I remember seeing a programme once where someone had a similar problem. They put a flourescent dye into the drain that they thought might be causing the problem, then checked the water that was coming into the sub-floor area beneath the house for traces of the dye.

Not sure that this would work with something fast flowing like a public sewer - I think the above may have just been on the soil pipe for that house - but it might be worth investigating further with the water company.