Severe water hammer after new combo

[Philip74]

Hi,

Just paid £3,200 for a new Worcester combo in our newly purchased 1920's home. There was one new rad put in at the same time, next to the new boiler. We fired it up for the first time properly a few nights ago and after about 30 minutes there was severe banging coming from several places throughout the house - this is REALLY loud. Obviously I'm concerned that this may cause a leak so I turned off the heating sharpish.

After doing some reading, I noticed that the radiators are heating up on the opposite side from where the thermostatic valves are. These valves have an arrow on them and I presume this means the flow of water should come from that side.

Is it actually possible that this plumber was so incompetent that he has plumbed the system in the wrong way round and the banging noise is coming from the water flowing through these valves the wrong way and subsequently shaking the pipes?

I should say, the new rad does appear to flow the right way.

He seemed in an extreme hurry and was 'between jobs'. At one point he put a nail straight through a pipe as well!

he's coming back on tuesday to have a look at the problem and would like to know if there is something else which could be causing this...

To make matters worse, since the install we've laid wooden flooring down at the cost of about £1000.....:dead:

 

[lame plumber]

some trvs are bi directional and some arent, hence banging, and some bi directional ones hammer any way when they reach temp and start to close. whole system needs checking out that the trvs are in right place and workling ok. may be case for drain down and valve swaps, not an issue with flooring, I am surprised this didnt occur when laddie was setting up the system post install when he checked all the rads were working ok and the system was balanced.

 

[Reg Man]

If it is not the TRV's, you may consider installation of a shock arrestor on the mains inlet to the boiler.

 

[kris]

Yeh im with the guys on the non directional older TRVs, another possible cause could be a mixer shower, if you have an existing shower not suitable for high pressures it may cause water hammer, youl know if its the trvs as will only happen when heatings on, you say theres an arrow on the valves is it one arrow or two, your plumber may have mixed up the flow n return,

 

[kris]

Forgot to say Philip welcome to the forum,

 

[Millsy 82]

I like the way you say that he is incompetent straight away. It is a mistake and it happens doesn't mean he is incompetent!! I have done it a couple of times usually if I was rushed on a job.

If you made a mistake in your job would you like to be called incompetent? I doubt it very much! So let him come back and sort the problem for you.

 

[Dotty]

Let your guy take a look.

That he's agreed to return smacks of integrity and competence.

 

[stevetheplumber]

take all the trv heads of and replace one by one over the next few days so you can help your installer find which are causing the problem could be just on or there could be more

 

[happyflyer]

take all the trv heads of and replace one by one over the next few days so you can help your installer find which are causing the problem could be just on or there could be more

Good idea Steve :24: elimination is the name of the game

 

[Ermintrude]

Have all the rads got trv's and no external bypass?

 

[tolly]

I thought Vauxhall made combo's

 

[Ermintrude]

It's TRVs man. Them the cars

 

[happyflyer]

Have all the rads got trv's and no external bypass?

Getting closer Ermi

 

[Reg Man]

Its them convi TVR's with an enormous 400 BTU's available on the rear.

 

[Kev the gas]

If it is not the TRV's, you may consider installation of a shock arrestor on the mains inlet to the boiler.

Worcester Installation instructions have insisted on a shock arrestor for years for properties with water meters, of course not many bother to read them !

 

[Reg Man]

Worcester Installation instructions have insisted on a shock arrestor for years for properties with water meters, of course not many bother to read them !

Exactly why I highlighted it. Hardly ever see them used, but are required by many manufacturers. Used to mention this to installers when inspecting their work and got a lot of stick for it, so gave up on the topic.

 

[leelister6]

I generally put new TRV's on during a boiler swap anyway unless the existing are fairly new and bi-directional. The system's drained down and it puts your mind at rest that they won't leak. As for calling him incompetent, bit unfair matey, if the valves were existing, they were the wrong way round to start with.

 

[Philip74]

Thanks for all you advice. Unfortunately the plumber hasn't made it back yet but I'm on a promise for tonight. A further quick question, I don't really want a 'quick' fix, I want the 'best' fix, therefore, would it be best to replace the unidirectional trv's with good quality bidirectionals or to actually fit new trvs onto the correct side of the radiators i.e. the 'flow' side?

 

[leelister6]

Finding the flow and returns can be a bit of a drawn out job - turn on heating and feel which pipe warms up first, sometimes you can't get round all the rads before the pipes are both hot or clip a differential thermometer on each rad. Most TRV's are bi-directional nowadays so if you get new valves fitted the problem should be solved. This will mean draining the system again so ask him to add inhibitor when refilling

 

[stevetheplumber]

Finding the flow and returns can be a bit of a drawn out job - turn on heating and feel which pipe warms up first, sometimes you can't get round all the rads before the pipes are both hot or clip a differential thermometer on each rad. Most TRV's are bi-directional nowadays so if you get new valves fitted the problem should be solved. This will mean draining the system again so ask him to add inhibitor when refilling

shut all the trvs down except one fire boiler check orientation of first rad then move on, opening and checking each rad in turn

 

[Philip74]

Thanks. I've found the flow and returns for the four rads and in each case the TRV is on the wrong end. I really just wanted to know, if he's going to put new TRVs on anyway, would it be better to stick them on the flow end, or, as they're going to be bidirectional ones, he can just replace the ones which are currently on the return end (i.e. the 'wrong' end). Hope that's clear..

 

[Millsy 82]

If it is only 4 valves it is probably best to replace them. If it was all of them it would be best to re-pipe flow and return on boiler. Have you had the system changed from a vented system to a pressurised system? This can cause it at times on old systems.

 

[Ermintrude]

They shouldn't all be trvs!!!

 

[Philip74]

Thanks for all your posts. Most helpful. The plumber came back and changed the four older TRV's for four new Honeywell ones and this resolved the problem. So, I guess the issue was being caused by unidirectional TRVs trying to close against the flow of water. Credit to him for sorting it out promptly.