We have a leak outside and can't find its source. What sort of expert to we need to talk to?
Our house is semi-detached. Both houses have a kitchen extension. neighbour's extension is newer and goes up to the property boundary. Our kitchen doesn't and we are wanting to build up to the boundary to widen our existing kitchen. There is currently about 1.5 metres between the two existing extensions.
When the builder dug two test holes to check the depth of next door's foundations, one in the corner between next door's extension and the back wall of our house and another approx. 1 metre along the side of next door's extension, he hit water 18 inches down in both holes. The corner hole continued to fill slowly when the water was bucketed out and appeared to be seeping in from between next door's extension and our back wall foundations. The water is collecting where part of the foundation needs to be laid. Meanwhile the second, smaller hole appears to have dried up now with no sign of water. This hole is close to where the shared drainage goes underneath both extensions.
Not knowing what the precise cause was, we then consulted a drain specialist. He identified a blocked drain (which he cleared) and then quickly cctv'd the drains. Having done this he identified a possible hole but was loathe to think the hole water was coming from the drains. He also said that as it was a shared drain with next door, Thames Water needed to have a look.
Thames Water's engineer surveyed the drains and confirmed there was a hole. He wasn't overly interested and by not reporting it was doing us a favour and that we should get someone to repair it privately.
We then brought in another drain specialist to do a report and cctv recording of the drains which identifed a hole but also a junction residing below our house. The report is intended to give us the proof for going back to Thames Water to sleeve the hole. The specialist also said that the drain damage was unlikely to be the cause of the water.
We also had a leak specialist visit. He was pretty much 100% sure that the water was either drain or ground water. He ran various checks including using gas in the mains supply for both us and our neighbours and coudn't detect any leaks from the mains water supply. He also tested for chlorine and found no trace which led him to believe the source of the water was either a spring or drainage.
We've also subsequently tested the water ourselves and again found no trace of chlorine or coliform bacteria.
My husband then decided to dig the original hole even deeper to try and identify the source. After digging, he noticed that the water had stopped coming in from the far corner at the opposite end of the hole. And like before it was coming in on the left hand side as you look at the back of the house.
At the moment we're stuck, having spent £1200 so far and still not definitively determined the source of the water. We don't know where to go next with this. Searching on the internet is proving quite frustrating as we can't determine the next steps. Next door are also concerned as the leak specialist gave their house a clean bill of health and until we identify the water source it could be coming from underneath either property. Hubby and builder both suspect that the water is coming from next door as the trickle always seems to be coming in from their side but water takes odd paths sometimes so we're not assuming anything.
I'm hoping someone on Mumsnet has had a similar experience of this type of building issue and can suggest what kind of specialist to speak to next. My husband thinks some kind of water pump and tank might be the solution but it's finding someone that can look at the problem and suggest a solution. Our builder is trying to help but hasn't faced an issue like this before so is limited in the help and advice he can give us.