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Knocking sound when turning on cold water

When I turn on my cold water I get a loud knocking sound which I believe is to do with pressure and air pockets. Hoping someone has some tips to avoid having to get the pricey plumbers out.

I've tried turning off mains, expelling all water from the lowest point and leaving it open then turning the water back on (or something to that effect (sorry I did it a couple of months back)) and it seemed to help but not resolve and the issue seems to be worsening again.

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Comments

Darren

Hey Pete,

We had a similar issue a few months back but it occurred when we turned our hot water on. Turned out there was an issue with a valve in our hot water service, which required a visit from a plumber... Hope you can find a solution to your water woes!

Dave

hi @ProjectPete

im no pro when it comes to plumbing - but had a similar issue. "water hammer". could be because there is too much water pressure and/or your pipes are not fixed properly. if you can get access to the pipes you can check it and use saddles to fix the pipe more securely.

if your pipes are secured you may need to consider getting a plumber in to reduce the pressure for you.

alernatively if it is not a mixer tap - you can get tap valves that help with this problem at most hardware stores.

Fyre

Is it only happening with one set of taps?. ie. Is it just the taps that go into your washing machine or dishwasher for example?. That would be water hammer and easy fixed with some anti water hammer valves which just screw in between you tap head and connecting pipe.

If it is happening to all taps and if you have the traditional spindle tap handles, water hammer won't be the issue as you aren't shutting off the water flow quickly.

May pay to get under the house or in the roof and get someone to replicate the issue. Could very well be a loose pipe.

All else fails, call in a plumber.

ProjectPete

https://www.workshop.bunnings.com.au/discussion/comment/88#Comment_88

It happens on all cold taps, both mixer and spindle. Interested (for me anyway) if I turn hot on first on the kitchen mixer for example then switch straight to cols, I prevent the knocking sound.

To be more specific, the knocking sound occurs when first turning cold water on and stops by opening the tap further, or by waiting it out for 5 seconds or so.

Knocking also happens (intermittently) when flushing the toilet.

ProjectPete

https://www.workshop.bunnings.com.au/discussion/comment/88#Comment_88

It happens on all cold taps, both mixer and spindle. Interestingly (for me anyway) if I turn hot on first on the kitchen mixer for example then switch straight to cols, I prevent the knocking sound.

To be more specific, the knocking sound occurs when first turning cold water on and stops by opening the tap further, or by waiting it out for 5 seconds or so.

Knocking also happens (intermittently) when flushing the toilet.

Helen

https://www.workshop.bunnings.com.au/discussion/comment/88#Comment_88

So helpful, thank you for this post! I have this problem since I got my new LG front load washer, it is only for the start of a wash, then it is fine. Reading your post I understand what is happening & will check out these anti hammer valves at Bunnings.

Ankitannex

https://www.workshop.bunnings.com.au/discussion/comment/62417#Comment_62417

I'm having exactly same problem.. I hear sound when i turn on cold water. It happens with all taps and same as yours, flush8ng toilet, running washing machine, using outdoor garden hose...

Did you end up fixing it?

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/96394#Comment_96394

Welcome to the Bunnings Workshop community @Ankitannex. It's fantastic to have you join us and many thanks for your question.

Let me mention @ProjectPete to see if he can give us an update on this situation and whether there was a solution.

We look forward to hearing all about your projects around the house and garden and would encourage you to let us know if you ever need assistance or had something to share with the community.

Mitchell

redracer01

https://www.workshop.bunnings.com.au/discussion/comment/62418#Comment_62418

Hello @ProjectPete

I know this thread has been over a week. Might I suggest this beauty! Place it at the most persistent tap that has knocking on it. It should fix the problem.

Cheers,

Red

Screenshot_2020-08-30 Sioux Chief 15mm Size A Hydra-Rester Water Hammer Arrestor With Conetite Tee.png

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/96438#Comment_96438

@redracer01,

I'm not sure about Pete's situation but I know @Ankitannex was certainly looking for a solution for the same issue recently.

This could solve their issue, many thanks for sharing.

Mitchell

ProjectPete

https://www.workshop.bunnings.com.au/discussion/comment/114805#Comment_114805

It became more intermittent over time so I ignored it then sold the house to my mother-in-law so I never actually solved it.

She ended up having a burst pipe in the roof space and when the plumber came to fix that she mentioned the knocking to which he blamed the high water pressure from the mains. He turned that pressure down and she hasn't had a problem since.

micheleBB

https://www.workshop.bunnings.com.au/discussion/comment/125231#Comment_125231

Had the same issue as well, had a plumber came and did install a water pressure valve in the main meter, still has not much changes. It did reduce the noise when running wash machine and that is it. Still noise when turning on some cold taps, flushing toilet, any advice or tips pls?

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/132368#Comment_132368

Welcome to the Bunnings Workshop community @micheleBB. It's wonderful that you've joined us and many thanks for your question.

You can try purging the excess water from your lines. The air in your lines provides a cushion that stops violent water hammering. Turn your mains water off and then flush the toilet and open all taps in the house to drain the water. Once this has been done, turn the taps off again. Turn your mains supply on slowly so it fills your pipes. Alternatively, you can try the opposite. Turn the mains off, open all taps and allow the water to flow out. Turn mains back on slowly until the taps all run freely, then turn them off.

You can also check to see if any loose pipes need to be fixed more securely or try changing the tap valve washers out to a different style. I managed to reduce some noise by installing Kinetic 12mm PVC Anti-Hammer Tap Valve - 2 Pack

Please let us know if that makes any difference.

Mitchell

micheleBB

https://www.workshop.bunnings.com.au/discussion/comment/136539#Comment_136539

Hi, Mitchell, thanks for tips and appreciated. Just a quick question: do I just need to run the cold tap water Or run both cold and hot tap water to remove the water hammer? As I only have issues with cold taps. And any tips to check the loose pipes as they are in the wall? Thanks heaps!

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/139425#Comment_139425

Hi @micheleBB,

If you only experience the water hammer on the cold line, try purging with just the cold taps. If there are loose pipes within the wall, installing a pressure reducer or water hammer arrestor might be a less costly operation.

Water hammer is caused when a pressure surge or wave of water is suddenly halted by shutting off a valve. Air is compressible and acts as a shock absorber within the system. When the air leaks out, and only water is present, it slams into your valves when you shut them off and creates the knocking or water hammer. In older houses, vertical sections of pipe were added to the system to act purely as air chambers. Newer houses use water hammer arrestors which are cylinders that hold air and act as a shock-absorbing piston.

Mitchell

micheleBB

https://www.workshop.bunnings.com.au/discussion/comment/141359#Comment_141359

Thanks, we had a plumber coming and installed a pressure reducer at front meter a couple week ago. It did reduce the noise when running the machine but that was pretty much. I will try to purge highest and lowest tap water out but still no changes; will do all cold water out this weekend and also to check the water hammer arrestors at Bunnings this weekend. Thanks!

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