Cold water pipe problem

[Carobee]

Hello,

New member, and non plumber, here looking for advice.

Live on second floor of a house converted into three flats, one per floor; the loft is above us. Our flat has one kitchen and one bathroom. The kitchen cold tap runs off the mains from a pipe that enters our flat from the loft; it being an old house conversion (1950s) the kitchen hot tap, the two mixer taps in the bathroom (bath and sink) and the toilet cistern run from a storage tank, also in the loft. There are two stopcocks in the loft; one to the kitchen cold tap on the mains pipe and one off the storage tank.

In recent weeks the pipe to the kitchen cold tap has been making a loud sound, after the tap is turned off, as if there is something solid that moves along the pipe and then back again; sort of like a heavy air bubble!! This is within 3 metres of the tap itself. At no time when the tap is turned on does the water splutter and it flows freely with no loss of pressure.

I did some research and wondered if it was water hammer but I do not think that it can be as the sound does not just happen the once after the tap is switched off, but will then randomly happen for up to a couple of hours or so afterwards! It also could not be described as a bang.

I tried switching off the stopcock and then turning the tap on to clear the pipe, but no water runs at all when I do that so the pipe is not emptied. I have not opened the stopcock as wide as it was to see if that sorted the problem but it did not.

So, does anyone out there have any ideas about what it is and, even more importantly, how to cure it!

Many thanks in advance.

 

[PlumbersMate]

The noise reoccurring could be neighbours shutting off their taps if its a shared main

 

[Reg Man]

Could also be water hammer on the float valve to the storage cistern. I would ensure that that pipework is properly supported and not touching up against joists or similar, also make sure the pipework is fully lagged with proper foam type insulation. Check the water pressure and fit a pressure reducing valve and non return valve if necessary.

 

[Carobee]

Thanks for the early responses. In answer to the suggestions
1. Neighbours: it is not a shared pipe.
2. Float valve in cistern: The cold water to the kitchen tap does not run from a storage cistern. In relation to the stopcock on the cold water pipe to the kitchen, I have not fully reopened it to reduce the pressure.

 

[Aquazone]

Not fully opening the stopcock will not reduce the pressure in the pipework, it will reduce flow rate. A pressure reducing valve like Reg Man says will reduce the pressure if thats your problem

It may be the ball valve in the cold water cistern, when you reduce the pressure by opening kitchen tap, the diaphragm vibrates in seating?

Might be better to get a decent plumber in, as you may end up chasing your tail

 

[Carobee]

Not fully opening the stopcock will not reduce the pressure in the pipework, it will reduce flow rate. A pressure reducing valve like Reg Man says will reduce the pressure if thats your problem

It may be the ball valve in the cold water cistern, when you reduce the pressure by opening kitchen tap, the diaphragm vibrates in seating?

Might be better to get a decent plumber in, as you may end up chasing your tail

That may be the way I have to go but, because of the rather simple arrangement of the supply to this tap, I am hoping it is something reasonably simple. For example, as stated, there is no cold water cistern! Pipe runs into the loft from outside the property. The pipe then supplies two storage tanks (one for our flat, one for the flat below, and a small central heating cistern. After all of those the pipe then runs to a stopcock and then on into our flat. Shutting that stopcock only stops the water to the cold tap in the kitchen. There is no cistern between the stopcock and the tank.