My cold water pipes are banging!

[briggal1]

Hi

I wonder if anyone can help.

We have lived in this house for the last 21 years and have never had a problem with banging water pipes until a few months ago!

About 8 or 10 years ago we had a water meter fitted, the type that replaces the innards of the stop cock on the footpath. again no problems with baning pipes.

sometime last year when it was really quiet at night we could hear a noise which sounded like running water and after this went on for some time I eventually traced it to a leak on the water meter. I called Yorkshire Water who came and replaced the water meter with a different type.

It was at some point after the replacement of the water meter that we started to notice banging after we had used the cold water. This isn't 'water hammer' as I understand it when you close the tap you get a bang in the pipes!

What we get is: After we run some cold water and then shut it off about 3 to 6 seconds after the tap is closed we hear a slight knocking noise then 3 to 6 seconds later another one and this goes on for variable lengths of time until it finally stops.

After searching on the internet I have shut off the water at the internal stop cock and opened all the cold water taps, flushed the toilets and run some hot water in order that the ball cock in the header tank opens. once the water stopped running I turned on the water at the stop cock and starting at the lowest tap closed each one when water was flowing without spluttering.

This appeared to solve the problem but after about two days the problem was back so I went through the same procedure with the addition of leaving the taps open to drain for a longer period of time until there where no drips. This again seemed to work but after about a week we are back again to the banging!

Any help you could give to solve this problem would be greatly appreciated as it's starting to drive me mad!

Thank you in advance for any help.

 

[classic33]

https://www.pistonheads.com/gassing/topic.asp?t=1258571

 

[briggal1]

Thanks for this classic33 I will investigate further.

 

[fossyant]

Have you got an open system with a header tank in the loft. In our case it was the rubber fill valve that had perished/got stiff and caused the banging. Changed with a quiet fill valve (same as whats in the loo)

 

[briggal1]

Hi fossyant, thanks for your reply.

Yes, it is an open system with a header tank. I have been up and listen by the tank and it doesn't seem as loud there but it's something I can investigate.

Thanks again!

 

[neil_merseyside]

Have you got an open system with a header tank in the loft. In our case it was the rubber fill valve that had perished/got stiff and caused the banging. Changed with a quiet fill valve (same as whats in the loo)

Similar to this is if the loft tank is losing strength/support (rare), or has moved from being emptied and resettled?
So the ballvalve either closes harshly as mentioned from knackered washer and this causes ripples so the valve pulses a bit until the waves settle a bit or the valve is wedged shut being slightly over filled. Or, the wobbly sides allows the same ripple effect from even a good condition ballvalve.
Back in the day it was common to tie an empty yogurt carton to the ballvalve arm to damp the arm, then a fancy plastic plate became available to do the same - then someone finally perfected the silent fill ballvalve (torbeck etc).

 

[briggal1]

Hi neil_merseyside thanks for your reply.

Thinking about it the header tank in the loft will only come into play when the hot water tank level drops. The problem I am having only happens after we run cold water so the ball valve should remain closed on the header tank, as I understand it.

Thanks again

 

[Tigerbiten]

Been thinking on this .....

It could be something like a very slow leak in one of the cistern valves, cold water/toilet.
So slow it's unnoticeable, stops when the pressure drops when you run cold water but starts again when the pressure rises after the taps close.
At a set pressure the leak resonates in the valve hence the noise.
I'd go around and change all the cistern valve rubbers and see if this solves the problem.

Luck .............

 

[briggal1]

Hi Tigerbiten thank you for your reply. I will have a look at this.

Thanks again

 

[Globalti]

From the symptoms you describe in your first post it's definitely a worn valve somewhere in a storage tank like a WC cistern. Have you got hidden tanks for your WCs? These are designed to leak into the pan if the washer perishes but you won't see the tiny trickle of water unless you hold a wad of bog paper against the back of the pan and it gets wet.

Otherwise it's a washer in a conventional valve somewhere, either worn or perished or damaged by dirt dislodged when they changed your meter. Does the water meter turn slowly even when nobody is drawing water? If so, there's your answer.

 

[TissoT]

Try turning the water pressure down a little at the stop cock.

Sometimes the knocking can be high water Pressure coming into the house.

 

[Globalti]

That's a good suggestion.

 

[newts]

Incoming mains pressure fluctuating at different times of day due to demand can be the reason for sporadic water hammer. Some cheap float valves are notorious for being noisy as they shut off, normally supplied on unbranded cheap sanitary ware. Quarter turn ceramic disc tap valves can cause knocking as they abruptly stop water flow. Poorly secured pipes in floor & walls amplify the issue.
Turning the stopcock down only reduces water flow rate & not static pressure.
Domestic water pressure is best around 3 bar, if your incoming mains is far higher than this it's a good idea to fit a pressure reducing valve near the stopcock (relatively cheap option for diy fit).
Torbek float valves used to make a 'squeaky farting' noise just before they closed off as the pressure balanced in the valve