Very loud water hammer in bath/shower plumbing

Kovan · Dec 10, 2019

Hi All,

I have plumbed my bathroom myself. I initially wanted to install a shower and bought a 2 outlet triton digital shower, midway in and I changed mind for a bath shower while the plumbing for the shower was already done. The digital valve was installed in the loft, 1 outlet to ceiling shower head and the other to handheld shower head. To add a bath filler, I split the handheld shower outlet into 2 outlets by installing a 2 way diverter valve on the bath rim, which made the pipe run more complicated and longer. Now when I divert water to the bath filler and shut the digital shower off, I hear a loud bang in the pipe work as if two pipes are hitting each other very aggressively. The ceiling shower head and the handheld shower shake as well when the digital valve is turned off on them but not as loud as the bath overflow filler. I can only see the inlet pipes to the digital valve shaking when the hammering happens. I have mains supply water which its pressure seems high and a combined boiler, the loft pipework is not clipped properly. The run from the divertor valve to the bath filler is in plastic pipe and the rest are in cp. Any ideas?

JCplumb · Dec 11, 2019

If you didn't get water hammer noises before the work then you probably just need to clip your pipework to reduce movement, if that doesn't work you can fit a water hammer arrestor to the cold feed pipework.
You say you have a combination of plastic and cp pipe, how have you joined the cp pipes to plastic?

Kovan · Dec 11, 2019

JCplumb said:
If you didn't get water hammer noises before the work then you probably just need to clip your pipework to reduce movement, if that doesn't work you can fit a water hammer arrestor to the cold feed pipework.
You say you have a combination of plastic and cp pipe, how have you joined the cp pipes to plastic?

I haven’t lived in the house (renovating it after buying) to see if the rest of the pipe work are okay, although I have no problem with the newly plumbed toilet, which is fed from the cold pipe before the digital valve. Also I did notice few times one of the kitchen sink pipes rattling very loudly. The plastic pipe from the diverter is connected to the filler using compression fitting. The handheld shower head is half plumbed (between diverter and head) using plastic pipe as well, the connection is made between the plastic pipe and the copper pipe using a compression stop valve. Thanks