Water Hammer

Eldi_Dos

Some of the modern washing machines that weigh the laundry to work out how much water is required can make noise like you describe.
Could find out if someone got a new machine in February.

twopenny

"Yesterday it was in the evening till 2300. Some days it’s all afternoon."

Process of elimination if you are sure it's someone else. All evening or all afternoon sounds too long for a dishwasher. Would they be putting on a long wash every day?

Do you use any of your appliances, run water at the times before or during hearing it?

Does running your water cure it?

Or is your water affected in any way during the noise?

I get the fog horn noise from my neighbours en suite. Mine makes it but not if I run the taps briefly before flushing the loo. She can't be bothered but it was ages before I realised it was echoing in  my wall - 2 garages between us and not in level with the en suite so must be a problem in her loft.

SaulGMan

We’ve run our own taps whilst the knock knock happens, no change. Plus we don’t have appliances running that late into the evening. 

Our water supply seems to run fine only concern is that I can feel the knocking in our pipes

subjecttocontract

My experience has shown there are 2 main things to reduce water hammer:
* Fit a new ball valve in the water tank.
* Turn down the water pressure.

FFHillbilly

subjecttocontract said:

* Turn down the water pressure.

turning down the water pressure will only work if the problem is after your stop tap (assuming thats what you mean by reducing the pressure, closing the stop tap slightly)

FreeBear

SaulGMan said: The sound is a knock knock and occurs every 5 to 10 seconds. Which is why I’m thinking an appliance like a dishwasher or washer.

About the only thing that springs to mind that might produce a regular and continuous pulsing sound would be a sprinkler system. Any neighbours using one in their garden at the time of the noise ?

gm0

As with the kitchen tap example upthread.  Shower mixers can also be the culprit in some systems. 

We had an old simple mixer with dubious non-returns. Failed.  Caused no end of issues with hot + cold hammer interaction with daily cool down and warm up of DHW. 

Probably wasn't the right shower in the first place for the system context.  But the developer had a box of them etc.

So it doesn't need to be a new appliance dated to when it started being noisy.

SaulGMan

Update 
I wrote to all 16 neighbours, 4 of which I believe are on a different water supply. 

Only 3 have not bothered replying. The rest have. 
5 have responded with no hearing the dunk dunk or knock knock, and 4 (including me) can hear the water hammer. The 4 are all next to each other. And I have been assured that they have all attempted to clear the pipes of any trapped air. 

But it’s still happening.
Getting very frustrating. 

I’m contacting the water board to see if I can find out who is sharing our water supply and then tackle it again.