DIY Doctor

Regular Thud in Mains Water Pipe After Boiler Fitted and Plumbing Work

Postby David Coe » Mon Feb 15, 2016 9:46 am

Hi there,

In need of some help. I recently had a new boiler fitted and new pipework fitted across to a new kitchen.

The mains water still comes in in the same place through my loft space and down 2 metres in a large cupboard into the floor where it then goes back up into my combi boiler and a t across to my cold tap which is approx. 3 metres from my cupboard.

Gas safe plumbers fitted the boiler and plumbing and tested it and ran water through the hot and cold copper isolator taps at the time of installation and everything worked fine.

Since then a plumber has connected up the washing machine, dishwasher, cold & hot tap and an outside tap. The outside tap goes through a brick wall under my sink and down another storey on the outside of the house, because I am on the 1st floor. The outside tap has insulation around it.

Since opening up the taps and starting to use my kitchen properly I have developed a thud like sound at regular 5 second intervals during sporadic periods in the mains water pipe that comes down from my loft space in the cupboard. The thud happens when nothing is on, so no taps are running etc.

The gas safe guys originally fitted a stopcock the wrong upside on that pipe, so originally I thought it was that that was causing the thud. They cam back and swapped it round but I still have the same problem.

I didn't use the outside tap for a period of time and it seemed to stop, then yesterday I ran that tap and later on in the day it started again.

It usually happens late on in the day. I have come to the conclusion it could be something like:

1. The pressure in the pipe is changing with the temperature outside and working its way up through the mains pipe.

2. Too many bends in the pipework under the floor?? (I hope not as it is tiled)

3. My stopcock which is further up the chain is a little weepy, could be the cause. I am going to get this changed anyway.

4. The only valve on that mains pipe from the ceiling to the floor in the cupboard is a stopcock, a different plumber said to put a ball valve on it instead, could a stopcock cause it to jault. I have changed the stopcock to a new one. The pipe still thuds.

Any help or ideas on this would be really useful.

Thanks in advance.
David Coe
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