Spotting mains water leaks

Spotting mains water leaks

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Jeff Howell’s Wise Howell column for Professional Builder returns as he continues to tackle mains water leaks.

Last month I wrote about mains water leaks, and the fact that Thames Water (my supplier) had gone to the trouble of sending one of their valued employees round to warn me that one of my WC cisterns was engaging in the “trickle down” effect (so beloved of our politicians).

It got me thinking of the time when I first started investigating dampness problems in buildings. It was August 1995 and the UK was in the grip of a heatwave and a drought (sound familiar?)

It hadn’t rained for months, and the clay soil in London was parched and cracking. Parks and gardens were shrivelled and brown. So why was my next-door neighbour’s front garden looking so green and luxuriant? It was like the tropical hothouse at Kew Gardens.

I’ll be honest – the talk was that she must have been breaking the hosepipe ban by sneaking out in the middle of the night to water her plants.

But more to the point, given that it hadn’t rained for so long, and the ground was so parched, how come my own coal cellar was smelling so damp and musty?

Thanks to an inquiry by a local radio reporter, a few of us gathered one afternoon in front of my house to record a piece about the misdiagnosis of water leaks as so-called “rising damp”. I remember that Roger Bisby – of this parish – was one of the assembled throng.

Long story short – Thames Water investigated and found a significant leak in a mains pipe under the pavement, on the other side of the road, about 20 metres away. The whole of the area – below the tarmac and concrete paving slabs – was sodden.

That was the start of my interest in mains water leaks, and when I learned to distinguish a “gusher” – where water visibly spouts up in the air – from the more usual gradual below-ground seepage.

I was reminded of it just recently, when a new neighbour asked for help in how to deal with a “damp” problem. She showed me the offending area – a patch of peeling emulsion paint and pink gypsum plaster against an outside wall in the utility room. Could she just paint over it?, she asked.

So these days I always start by looking for water pipes close to any dampness problems, and in this case there were several – the mains feed to the combi boiler, the flow-and-return pipes from the boiler to a nearby radiator, the condensate drain running out through the wall, and a mains feed to the outside tap, also through the wall.

There will need to be a bit of opening-up of the area to see which of these is causing the trouble, but my money is on the outside tap. I’d be surprised if Thames Water haven’t already got the house logged for a visit from the meter inspector!

If you have any building or tradespeople questions, E-mail Jeff via his website

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