HELP: Dripping or knocking sound under shower tray - advice sought

sirufus

We have just had someone gut and re-do our bathroom totally, and have just discovered there may be a problem.


When the newly installed shower in the bathroom (on the first floor) is turned on, then downstairs, in the room directly below the shower tray, there is a dripping/knocking sound, initially every 2 or 3 seconds, then about every 10 or so seconds while the shower is running. After the shower is turned off, then the drips/knocks occur less frequently, say one every 30 secs and continues for a few minutes. Has anyone experienced this and can throw some light about what is causing this please???

Could it be that the waste pipe may not be 100% tightly connected to the shower tray, or there is some other sort of leak. We have used the shower about 3 times and there is no water seeping through the study ceiling (yet), but maybe that is because it is a very small leak which may only cause water to leak through the ceiling in a few weeks or months, or may weaken the ceiling board, and we do not want to risk that happening.
A friend said he experienced a similar situation and apparently there is some type of liquid sealant called pig which can be injected into the waste pipe and will seal it up (kind of like Mr Muscle cleaning out waste), but the equipment to do this is expensive.


In order to be really sure, seems to me that either our installer would need to rip out the study ceiling to see what is happening, or rip out the newly installed shower which might not only break the shower but also some wall and floor tiles. Either way it is not looking good although ripping the floor of the room below may be the cheaper option.

Do you think this sounds like a leak, and do you have any ideas what might be the best way to proceed? We haven't paid the installer yet, as they haven't totally finished, and will look at the drip/knocking sound. If the problem hasn't been satisfactorily resolved by the end of the job what should we do with regards to payment??

Should work undertaken to fix it be done via the installer's insurance rather than getting them to remedy it?

If the installer damages the shower unit or tiles, or has to rip out the ceiling, that he should also pay for the damage and materials to make it as it was?


Would reaalllly appreciate and advice and suggestions on how to deal with this unexpected problem. And THANKS for reading this!:o

Halloway

Could the sound be caused by vibration of the water pipes and/or expansion of the hot pipe to the shower? I am not an expert but I don't think a water drip would have enough energy to be audible downstairs.

You could try some troubleshooting. Run the shower into a bucket for a while and check for sounds. Then switch off the shower and gently pour the bucket of water into the waste and listen for sounds again. That would at least narrow down the source of the noise.

sirufus

thanks for your thoughts and ideas - will try it out. by the way, there is no insulation between the floor joists, so there is nothing absorbent between the shower tray/waste/pipes and the ceiling of the downstairs room...

Traveller1981

I agree with Halloway, sounds to me like the expansion of the hot water pipe. I have the same in my house (new build). Got the plumbers out ot have a look at mine and after investigation turned out to be the hot pipe expanding.

sirufus

thanks for your post traveller, very useful indeed. could i ask what did the plumber do to identify that as the exact cause, and did anything have to be done about it? was it ok to leave it be and live with the poltergiest?

Traveller1981

Sorry for the slow reply, I forgot to check back on the thread. The plumber checked the soil pipe (had recently been resituated due to some other plumbing issue), so they checked the pipes and noticed there was a tight fit for the hot water pipe, so they made the hole a bit bigger and it lessened. We now only hear it occasionally - probably because we are used to it.
Nothing has to be done, but out of courtesy (due to the other issue with had) they made one of the holes that looked a bit tight, a little bigger.