Water coming in from neighbour, advice please

[bumpertobumper]

We live in a semi detached late victorian house. Next door is divided into flats which are seperately owned and rented out. We get on well with all the residents, trouble is with the downstairs owner...

We both have a cellar, ours is tanked, used at a utility room, and had a decent automatic pump fitted for just in case. This pump hadn't been activated for many years, until a couple of months ago... started going off several times a day pumping out tens of litres of water!

Transpired that neighbour's cellar is under several inches of water. After initial resistance, claiming that he didnt care that the standing water was there the owner eventually got a pump and emptyed it. Which stopped our pump going off too.

It became clear that when his cellar fills up, then the water comes through into ours. When his is empty, ours is fine.

He has had the water board make all the investigations they are willing to do, they did fix one leak but the situation continues. He is now pointing the finger at the neighbours on the other side, and still at the water company. Refusing to consider that the leak is on his property somewhere.

The leak is probably under his concrete driveway and so he doesn't want the cost of hassle of looking for it.

Meanwhile we continue to be concerned about the impact of all this flowing water on the structural integrity of our properties.

I have spoken to surveyors, structural engineers to get advice. They say nothing can really be done without invasive investigations but not by them. No clear guidance about what professional we need to find the source of the water.

This man is incredibly mean, grumpy, hard to deal with and never spends any money on his property.

So after all that background, my questions are:

• who can figure out where the water is coming from?
• what do i tell my building insurance? If i tick the box that says yes to having experienced flooding it triples my premium forever; if i say nothing and there are future problems caused by this or something else we may not be covered. Is there an option if i call them to declare - neighbour had a leak, came into me, no damage done cos I have a pump. ?

Would really appreciate the wisdom of MN right now... thanks

We have

I’d speak to your insurance company and they’ll pursue your neighbour if necessary. We had leak in our cellar that was resolved by our insurance company. Our premiums haven’t gone up that much. It isn’t a flood, it’s a leak.

Thanks Bent, that is good to hear

Yes don't tick the flood box because that's 'nature' and sod all you can do about it hence high premiums. Escape of water or leak are man made and can therefore be solved thus no long standing issue to be insured.

I would also dob him back in to the water board. I believe that they have the right to force repair if a property owner is wilfully wasting water (which he seems to be doing).

a plumber, including one who works for the water co, can track a leak in the suuply pipe by listening to pipes with an asssortment of tools varying from a simple stick to an ultrasonic detector.

They can also tell if the leak is from a supply pipe (chlorinated water) or a drain (soapy water) or a gutter (leafy water) or groundwater (mineral content).

The water co will be interested in this.

From what you say I assume the neighbours do not have water meters.

How exciting, MN royalty has commented on my thread 
Thanks @PigletJohn and others for advice.
I have been through the insurance policy documents and due to the nature of the situation we aren't covered, there isn't anything they would do.

So back to trying to persuade neighbour to get a decent plumber with the right kit to come around... fingers crossed

Will also talk to water co again to push them on what next steps are available. They currently saying they have checked their bit and trying to wash their hands of it. It is so frustrating

Are you sure that an issue which is being caused by next door is not covered by your insurance?