Groaning Pipes: unvented water cylinder

[Rick Webb]

Hi,

Firstly, what a great site, and thanks to all the hard-working and committed professionals who are prepared to take the time to offer advice.

I have a Range Tribune Unvented Electric Water Heater (with expansion vessel). It was installed approximately 2-3 years ago.

I recently had a plumber from a large reputable (but local) firm to visit to perform a service. I asked if he had an unvented certificate. As part of the service, I mentioned that the overflow occasionally leaked.

He checked the expansion vessel and the pressure was low. He restored the pressure to 3 bar.

After he had done this, the pipes started making an awful groaning sound every time the hot water was turned on, especially after the water heater is on. This lasts between 30-90 seconds.

After one week, the noise had not stopped, we called the plumber who came back out. He reduced the pressure in the expansion vessel to about 75% of what it should have been. He explained that if that didn’t fix it, the expansion vessel was probably faulty.

I have taken a video of the noise it makes:
http://www.youtube.com/watch?v=WuQuT7deA78

Given that the unit is less than 3 years old, and this problem had never existed before the plumber came out to it, I struggle with the notion that this is a faulty part.

Is there anything else this could be?
Any advice/help would be appreciated.

 

[cr0ft]

Hi, has the unit been serviced annually or is this the first time it's been serviced?

 

[Rick Webb]

This is the second service, and the unit is perhaps 3 years old. It has been serviced almost annually.

 

[Rick Webb]

After help from the Webmaster, I have been able to edit this post and include the link to the video (if this helps).

 

[stoker122]

I had a similar problem after servicing an unvented cylinder once, turned out to be a problem with the pressure reducing valve juddering, water hammer type thing.
We had to change it.