Knocking pipes

[blake616]

Help! I added onto my house last year and since I did, I have had a strange “banging” sound that recurs several times a day and seems to come from my pipes. I do not have steam radiators (heat pump), so it can’t be that, but I did install 3 slightly unusual bits: a TORO low-flow toilet, a european tankless water heater (Rinnai) and a multi-head shower (including a pressure-balancing loop).

NOTE: I didn’t do any of this, the plumbing subcontractor did. It also didn’t start immediately… it started sometime this summer (the construction was finished in Jan.)

My relationship with my contractor was strained at best (long story, but the construction tool >1 yr. for a 300 ft. sq. addition) so I don’t want to go to him unless I have some idea what I’m asking about. In fact, if it’s something simple I’d rather fix it myself.

Any ideas what I should look for?

Also, the noise seems to move around from room to room, though it’s nearly impossible to place where it originates. It’s pretty loud too.

A copy of the replies sent to [email protected] would be *much* appreciated!

Thank you in advance,

Gina

[NickHydroParticipant]

Tha rinni bang wen yuo brush teth an get cupsa watre tha flow to low

[IntrigueParticipant]

Nick, you said “Tha rinni bang wen yuo brush teth an get cupsa watre tha flow to low”

Do you mean that the pressure coming from the Rinnai is to low? It seems to happen (this knocking) whether the hot water is running or not. (In fact it was doing it Sunday morning when I was just laying in bed and there was nothing else happening!). Is there something I can do to fix it?

You can email me directly at [email protected]

Thanks,

Gina

[johnwsParticipant]

Is there a pressure reducing valve supplying the house? If there is, then is the pressure in the main supply (to the valve) less than the pressure the valve is trying to reduce to? eg. If the valve is set to 50psi and the supply pressure is only 45psi then you can get a knocking sound from the valve (some brands) when nothing is being used.

[SelgasParticipant]

The Rinnai water heater you have installed (you call them tankless units) is a mains pressure device that has no pressure reducing valves fitted in the line to it and is unlikely to be the cause of your problems.
The banging noises you are hearing are more likely to be those of fast opening or closing solenoid valves or loose fitting pipework.
Household items such as dishwashers, washing machines, wastemasters and the like often cause this water hammering by their electric solenoids slamming shut – effectively causing a water shock wave within the pipework.
Check if there are any of these type of devices fitted to any of your pipeline and then check if they are operating when such noises are heard.

[johnwsParticipant]

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In reply to message posted by Peter:
The Rinnai water heater you have installed (you call them tankless units) is a mains pressure device that has no pressure reducing valves fitted in the line to it and is unlikely to be the cause of your problems.
The banging noises you are hearing are more likely to be those of fast opening or closing solenoid valves or loose fitting pipework.
Household items such as dishwashers, washing machines, wastemasters and the like often cause this water hammering by their electric solenoids slamming shut – effectively causing a water shock wave within the pipework.
Check if there are any of these type of devices fitted to any of your pipeline and then check if they are operating when such noises are heard.

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Peter, she said that there were no fixtures operating at the time of the noise. If there were, I would agree with you that water hammer is the cause. However, the tankless system may have been added at the time of the house addition and there may have been a pressure reducing valve installed before then.
As I said, if the pressure upstream of the valve is less than downstream it can cause the valve to slam shut, this would cause the type of noise she is talking about. Removing the valve would be the solution (if there is one???).

[bungieParticipant]

Or the toilet cistern is leaking, the slow flow throught the inlet valve can cause a hammer sound, without any taps running

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DISCLAIMER

All advice is given with-out seeing the job, and hence all advice MUST be taken as advice with limited knowledge on the exact situation. NO responsibility can or will be taken. And yes, I am a licensed Plumber and Drainer with my own business in Brisbane Australia.
Try visiting ….
Macadamia nuts and Aussie products … Prostate cancer kills 2600 per/year in Australia … Ecommerce books

[SelgasParticipant]

Bungie

Yep u r right your fault finding is faultless!! dang Auzzies some of ya is really bright after all hahahahaha

[bungieParticipant]

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DISCLAIMER

All advice is given with-out seeing the job, and hence all advice MUST be taken as advice with limited knowledge on the exact situation. NO responsibility can or will be taken. And yes, I am a licensed Plumber and Drainer with my own business in Brisbane Australia.
Try visiting ….
Macadamia nuts and Aussie products … Prostate cancer kills 2600 per/year in Australia … Ecommerce books

[TheLocalPlumberParticipant]

Is there an expansion tank located on the cold water service to the tankless heater after the check valve?

Bill
The Local Plumber
Tustin, California

[Author]

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