water hammer

Hydraulic shock (colloquial: water hammer; fluid hammer) is a pressure surge or wave caused when a fluid in motion, usually a liquid but sometimes also a gas is forced to stop or change direction suddenly; a momentum change. This phenomenon commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe.
This pressure wave can cause major problems, from noise and vibration to pipe rupture or collapse. It is possible to reduce the effects of the water hammer pulses with accumulators, expansion tanks, surge tanks, blowoff valves, and other features. The effects can be avoided by ensuring that no valves will close too quickly with significant flow, but there are many situations that can cause the effect.
Rough calculations can be made using the Zhukovsky (Joukowsky) equation, or more accurate ones using the method of characteristics.

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  1. M

    Water hammer advice?? (I’ve checked old posts)

    Hi all. Just had a neighbour knock the door regarding a water hammer issue. My own house developed this issue sometime last year as well which is when the neighbours roughly started. Severn Trent were doing bits and bobs out in the street back then but this is probably a coincidence. Our water...
  2. C

    Water Hammer after new bathroom installed

    Hi I've recently had a new bathroom installed. I've noticed when I flush the downstairs loo there was a hammer type noise under the bathroom floor when the cold feed for the loo turned off/ same with the washing machine. So I turned off the mains water supply. Opened the highest tap first...
  3. M

    Bad case of water hammer.

    Hi everyone I have been a plumber for 3 years now, I haven't come across many issues with water hammer so I'm not to sure what to do. it happens on the hot pipework, more specifically the hot taps in the bathroom (basin and bath). but it only seems to happen when I open the hot tap to a...
  4. R

    Unsolvable water hammer when shutting taps

    I have read a few threads including one by Debbie Stano that were similar to my issue but that thread stopped a while back without any resolution I could see. I'm in Brisbane, Australia but I'm after general ideas from anyone here or in UK (I realise this is a UK based site). Point form...
  5. M

    Water hammer at same time every night

    I wonder can anyone give me some advice over what has become a very annoying situation? Approximately three months ago, what I assume to be water hammer started in the airing cupboard of my second floor flat. This manifested, and continues to do so, as a repeated, i.e. every 60 seconds or so...
  6. J

    Water Hammer - after pipe change

    Had two pipes changed - one cold and one hot. The cold had a leak and the warm was punctured and about to leak so both were replaced - about 50cm sections in each pipe. After that I started getting water hammer - banging of pipes. I've tried lowering the water pressure - that helps a bit but...
  7. T

    Water hammer when turning on taps

    I'm getting water hammer in three cold water taps when turning on. If hot water is also turned on there is no water hammer. Previously I was getting all sorts of noises from the pipes even when no taps were turned on. I ran all the hot water from the hot water system via the hot water tap...
  8. T

    Water Hammer problem

    We have had a minor water hammer issue for years but it was never really a problem until the last year or so. It is so loud it sometimes make you jump, it's driving us crackers. It happens sometimes when we use the electric shower or washing machine but then it's not at it's worse. It never...
  9. K

    New washing machine and water hammer

    I bought a new washing machine, it had bad water hammer and started leaking from the inlet valve (plus a couple of other issues) so I exchanged it for the same model. The new one seemed fine at first but after a couple of washes has water hammer. Is the problem with the machine do you think, or...
  10. Robcrick88

    Can you get water hammer when stopcock is off?

    Been getting water hammer everytime neighbour turns off their taps. Very loud in our house and have asked neighbour who denies hearing anything. I tried turning off my stopcock and switching off boiler for a few hours and could still hear the banging when they use their taps. Is it possible to...
  11. Chrisbarber

    Water hammer moved from washer to toilet flushing

    We recently, about 2 days ago, started getting water hammer from using the washing machine, this has been fixed by attaching an arrestor to the inlet hose which great. However we've now started getting it from the toilet completing a flush, which is upstairs and not near the washer. Is it normal...
  12. O

    Can replacement cartridges fix water hammer?

    Hi all, We have some terrible water hammer in our house. I've had a plumber come round to try and fix it, to no avail, but I'm not convinced he chose the right course of action. He started by checking the water pressure, securing a few pipes in the roof space which was fair enough, but...
  13. O

    Do new tap cartridges fix water hammer?

    Hi all, We have some terrible water hammer in our house. I've had a plumber come round to try and fix it, to no avail, but I'm not convinced he chose the right course of action. He started by checking the water pressure, securing a few pipes in the roof space which was fair enough, but...
  14. D

    Water Hammer following Combi boiler installation

    Worcester Bosch Greenstar i combi installed. Since installation water hammer happens when hot taps are turned off, but only when the heating is on. Have you experienced the sam?
  15. D

    Water Hammer on washing Machine

    Have a problem with water hammer on washing machine, solved it for a bit with a mini rester been thro 2 seem to only last a year or so and expensive. So purchased a 1/2" T and a 0.16L mini expansion vessel and T what pressure should it be set at? When I first used machine it seemed ok then few...
  16. J

    Quooker water hammer

    Greetings and Merry Xmas to all Just been to an interesting callout. Quooker fusion pro3 tap recently fitted in a new kitchen on a small 2 bed mid terrace with a Ideal logic 30 combi. Customer getting the most horrendous water hammer, started the day after the "plumbers" left for xmas...
  17. M

    water hammer after flushing toilet

    Hi, I have been having water hammer after flushing toilet in the past couple of weeks. I have tried turning off the stopcock and opened all taps to drain all the water in pipes and toilet. The water hummer then fixed for a few flushes but it comes back. It's ok a few weeks ago before we fixed...
  18. S

    Should a water arrestor be banging?

    Hi, I had a problem with water hammer where the pipes in my house would bang every time I turned a tap off quickly. I called a plumber and he advised fitting a water arrestor, which I'd heard about after looking the problem up online, so I agreed and had one fitted. The banging sound has gone...
  19. M

    Water hammer ceramic disc taps

    Can you get water hammer from ceramic discs on tap valves? Have been to a job where is it sounds like its coming from there. But I know this isn't always the case. Thanks
  20. P

    Inaccessible pipe: clipping vs support

    Hi, I managed to push two 15mm pex pipes through the underfloor space of a second floor. They go (on a straight run between two parallel joists) from a hole in the floorboard (18mm thick) under an existing radiator to another hole in the contiguous room's floorboard, ready to attach a new...
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