Water Hammer - Banging sound from taps when Shutting the taps off?

princeofpounds

greyteam1959 said:

The OP could try slightly closing the isolator valves on the appropriate taps etc.
Could possibly solve the problem for no money.
😁😁

This is really worth trying. The quarter-turn tap is closing quickly, presumably with plenty of pressure behind it, and that's causing a shockwave to travel back up the pipe. Narrowing the valve immediately 'upstream' of the tap can reduce that effect. I get water hammer in my property in the cold water system, the whole thing was solved by just slightly restricting the mains water valve to lower the pressure a bit.

Jeepers_Creepers

As PofP pointed out, this was almost certainly caused by the change from multi-turn 'washer' taps to 1/4-turn ceramic, which shut off the water supply 'too' quickly, causing that shock.

There may even be another underlying cause like the mains pressure being too high - say much above 3 bar. These shocks aren't just a nuisance, but can cause damage over time; they are best got rid of.

I think it would be useful to know what your cold mains pressure is like, because if this is way above 3 bar, then you'll still have a potentially-problem-causing high pressure even after you've hedgehogged your pipes with shock arrestors.

OP, did your plumber measure the pressure when he fitted your combi? If the pressure is a bit high, then a Pressure Reducing Valve will sort it - fitted just after the mains stopcock.

Or, your situation could be the complete opposite - there is nothing 'wrong' with pressures or flows or taps, but it's just a loose pipe that hasn't been clipped down properly on a longish run. Can you detect where the hammer is coming from?

Other than that, fit arrestors if you like, but it's definitely also worth trying PofP's idea of tweaking down each tap's isolating valves - turn a tap on full (it'll probably be running too fast for most purposes?) and tweak down the valve until it reaches a point you are perfectly happy with at full chat. That's a simple, no-cost solution that could work.

I wouldn't, tho', turn down the main stopcock as you really want to maintain the max flow to your house. If the problem is due to a too-high mains flow and pressure, the answer is to reduce the pressure, but not the flow. That's what the PRV does.

mazibee

Thanks everyone for the replies.

Please can some one suggest me how to check the mains water pressure,

I have no idea what was the mains water pressure when the Combi Boiler was installed.

I have also  checked and found that stopcock was turned  only 1/4 turn , even its not a one full turn

I have also noticed (as our boiler is installed in the left corner of the kitchen) three pipes that are going out from the top of the the boiler in  ceiling, two of the copper pipes are not secure and when holding them and then opening/ closing the kitchen mixer tap the bang reduces,

On the top floor underneath the carpet we have laid the sheets of 15mm ply over the floor boards to stop the creaking noises and unfortunately they creaks are also still there, now I have no idea how it can be fixed.

I will try to post the photos of the boiler once i am back at home.

Thanks again

Jeepers_Creepers

Mazi, is the ACTUAL hammering/banging coming from YOUR house or the neighbour's?

You measure pressure using a pressure gauge, and water flow by measuring the number of litres coming out your full-ion cold kitchen tap for 10 seconds. Times that by 6 to get 'litres per minute'. Open the stopcock fully before doing this.

The lpm will give us a good idea of what your supply is like, and just how wet your troos get in this process will be a guide as to the pressure. When you open the cold kitchen tap fully (with the stopcock also fully open) does the water balst out? Bounce off the sink bottom? Splash?

The fact your mains '!!!!!! was almost closed does hint at a high pressure/flow situation that someone tried to mitigate by this crude method. It's a bit complex, but closing off the stopcock will not reduce the actual static pressure, only the flow.

But please answer the first question first.

(This is a shared supply? Where does it split? Where does it come on to your or your neighb's land?)

mazibee

Thanks for your reply @Jeepers_Creepers

Actual hammering/banging is coming from our house.

Its not a shared supply.

It only happens when open/ close the taps ( Kitchen Mixer, Bathroom Sink Mixer ) and after using the toilet flush , bang comes when the filling stops.

Jeepers_Creepers

mazibee said:

Thanks for your reply @Jeepers_Creepers

Actual hammering/banging is coming from our house.

Its not a shared supply.

It only happens when open/ close the taps ( Kitchen Mixer, Bathroom Sink Mixer ) and after using the toilet flush , bang comes when the filling stops.

Argh - sorry, Mazi. Got you confused with another thread!

Your problem is either down to loose pipes, or an excessively high water pressure. To measure the pressure requires a gauge which you can buy in places like Screwfix and Toolstation. That your stopcock was almost fully shut does suggest, tho', that is your issue, and the solution is a PRV and - if needed - a shock arrestor.

Can you carry out the tests I suggested - measure flow, and wet yer pants?

Given that these two components are cheap to buy and would be fitted at the same time and in the same place, I would personally go with fitting both. Having your pipes being hammered and shocked isn't good for system longevity, let alone your peace of mind.

Could you DIY this? Have you cut copper pipes and fitted compression fittings before?

mazibee

@Jeepers_Creepers

Unfortunately I have never done that before,

I can measure the pressure as suggested.

For measuring the pressure , so I need to open the stock !!!!!! fully and then open the Kitchen sink mixer and measure the flow , also do I need to open the kitchen tap fully before measuring the pressure.

Our problem of hammering started after replacing the Kitchen Sink mixer tap

from this

https://www.screwfix.com/p/56a-deck-mounted-sink-mixer-kitchen-tap-chrome/3513T

to

https://www.screwfix.com/p/cooke-lewis-58a-deck-mounted-dual-lever-bridge-mixer-kitchen-tap-chrome/7390T

Jeepers_Creepers

mazibee said:

@Jeepers_Creepers

Unfortunately I have never done that before,

I can measure the pressure as suggested.

For measuring the pressure , so I need to open the stock !!!!!! fully and then open the Kitchen sink mixer and measure the flow , also do I need to open the kitchen tap fully before measuring the pressure.

Our problem of hammering started after replacing the Kitchen Sink mixer tap

from this

https://www.screwfix.com/p/56a-deck-mounted-sink-mixer-kitchen-tap-chrome/3513T

to

https://www.screwfix.com/p/cooke-lewis-58a-deck-mounted-dual-lever-bridge-mixer-kitchen-tap-chrome/7390T

Do you want an instant cure?! Peasy - just shut your new tap off sloooowly... Jobbie jobbed.

Your original tap operated in a very gradual way, so that steadily reduced the water flow, and hence the rebuild in pressure in the pipes was also gradual = no shock. Your new tap is 'quarter-turn', so shuts off the water very quickly = shock. 

It's not the tap's fault, tho' - there is an 'issue' elsewhere, excessive pressure or shaky pipes.

Meanwhile, for measuring pressure, you need a gauge. Not sure one's worth buying, so instead just use your gut. Open the stopcock fully, and then the kitchen cold - how forceful is it? How much bounce? Turn it off, place your thumb over the end of the spout, press hard, and slowly turn the cold back on. Can you hold back the water?

For flow, that's easy - stopcock open fully, pan under tap, open cold fully, and time 10 seconds. Measure the number of litres and times that by 6.

Regardless of all that, you have 'hammer'. So you need a PRV or a shock arrestor. I'd fit both - your system will thank you.

mazibee

Thanks @Jeepers_Creepers

I checked the water pressure by opening the stop valve fully, I attached the pressure gauge on the line under the sink

Working Pressure was 2 bar with cold water tap opened fully and the standing pressure was 4.5 bar when tap closed but the gauge needle jumped t and fluctuated before setting to 2 bar when I turned the tap off.

I also checked the flow of the water and it was 18litres per minute on the Cold tap and 10 liters per min on the hop water tap

Hammering sound is not coming when I am turning the cold water mixer tap quickly ,I think  due to the water hammer arrestor fitted on the cold line.

Hissing sound is coming form the mixer tap when the both cold / hot is opened slightly,

Also I tried to check the pressure in the Hammer arrestor vessel, on the label it says Factory setting is 3.5 bar when I checked it was 1.08 bar , it tried filling with the pump and still its gone to 1.4 bar ,

Any idea on how to fill this small 0.16 l Reflex Hammer water arrestor properly to 3.5 bars.

Strangely,  I also found that there are two stop valves under the sink, one just above the other with a small space in between them.

Any further suggestions keeping in view of the above findings.

Thanks in advance

Jeepers_Creepers

mazibee said:

Thanks @Jeepers_Creepers

I checked the water pressure by opening the stop valve fully, I attached the pressure gauge on the line under the sink

Working Pressure was 2 bar with cold water tap opened fully and the standing pressure was 4.5 bar when tap closed but the gauge needle jumped t and fluctuated before setting to 2 bar when I turned the tap off.

I also checked the flow of the water and it was 18litres per minute on the Cold tap and 10 liters per min on the hop water tap

Hammering sound is not coming when I am turning the cold water mixer tap quickly ,I think  due to the water hammer arrestor fitted on the cold line.

Hissing sound is coming form the mixer tap when the both cold / hot is opened slightly,

Also I tried to check the pressure in the Hammer arrestor vessel, on the label it says Factory setting is 3.5 bar when I checked it was 1.08 bar , it tried filling with the pump and still its gone to 1.4 bar ,

Any idea on how to fill this small 0.16 l Reflex Hammer water arrestor properly to 3.5 bars.

Strangely,  I also found that there are two stop valves under the sink, one just above the other with a small space in between them.

Any further suggestions keeping in view of the above findings.

Thanks in advance

4.5bar static is high. You will almost certainly notice a significant improvement if you fit a PRV and set it to, say, 3.5bar.

This shock arrestor has a Schrader valve on it then? When you were pumping it up, were you doing this against the pressure of the water on the other side? Do you know what make it is? Try and find the proper instructions 'cos I don't know.

Any chance of a photo of these two stop valves?!

The shock is caused by the change in pressure. Pipes have some flex and 'give' in them, very much so if they are plastic. When you shut off the water, the pressure jumps upwards, makes the pipes expand a tiny amount for a moment before they settle back to their original size = pressure swings and 'shock'.

Fit another shock arrestor on the hot side too I guess?!