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Hi PlumbersForums.

I've been having some issues with my central heating system in a 4 year old new build property for over a year now. I have some mental health issues with anxiety so this might be exaggerating the problem somewhat but please bear with me.

My issues start with Plumber A doing a service around early November 2018. No problems with the service or anything like that. A few weeks later I notice that the radiator in the master bedroom is now making a popping sound when the heating comes on. Not being so hot (pun not intended) on central heating I decided to bleed it see if some air comes out. Instead I find darkish brown water indicating corrosion. The system was fitted with the new build house back in July 2015 and filled with Sentinel X100. I call the plumber back up but he's not too interested in the findings.

I call in Plumber B who bleeds the water and agrees that there's been some corrosion going on in the system. He drains down the system, fills it back up and adds approx 750ml of new inhibitor into the system. It was after this I then started noticing that when the central heating system comes on it results in a very loud humming like noise that can be heard all around the house when the ground floor heating comes on. At one point when this noise was going on the central heating suddenly cut out as a result of a pressure drop. Plumber B advised I top up, which I did. Unfortunately this somehow resulted in a horrible stain appearing on my living room ceiling close to where the boiler cupboard is. Plumber B advises getting an emergency plumber out to look at it.

Emergency plumber is then sent out who cuts a few hatches in the floor above where the stains appears. Evidence of a leak is present but he can't find any fault with the pipework around it. A friend of mine who works for a well-known energy company suggests I put kitchen roll under the joints to test for a week but the sheets are indeed dry after a week and the pressure is holding.

I then notice that the vinyl floor under the radiator in the bathroom is warped. I pull it up and find evidence of a leak. I then call Plumber D who's actually very analytical of the problem. He looks under the hatches and notices that there's stains running down the plastic pipework from a radiator joint. He's absolutely convinced it was the source of the issue so knocks a hole in the wall to replace it. I ask him about the humming noise and he tells me it's the TRVs and to put them all the way to max (3 being the default and what the house builder advised setting them to).

Given I've had so much trouble with the bathroom (I had a leaky tap, leaky shower and now a leaky radiator) I had the bathroom pulled out July this year and a really nice one fitted by a very reputable company. They find another suspect joint behind the radiator and replace it before fitting the new radiator. They add in 250ml of inhibitor left in the bottle just to keep the system topped up.

I'm now in a state where the two radiators with TRV on the ground floor need to have the TRV set to max in order to avoid the noise. This doesn't fix anything in my mind just conveniently works around the issue without properly addressing it. I notice there's the ABV underneath the boiler set almost all the way to the right. Tweaking that a bit when the noise happens seems to make it go away.

The central heating system is a Baxi Duotech. I have separate Myson control panels in my master bedroom and living room. I have programmed temperature settings of 18C low, 20c medium and 22c high. The radiators are Myson radiators fitted with Myson TRVs except in the living room and master bedroom. The radiators in the living room and master bedroom do not have a TRV fitted. As best I can tell the TRVs are functioning i.e the radiators all come on or have any cold spots.

So basically...

1) Why could I have the TRVs set to position 3 when I moved in but now I need them set to maximum to avoid the loud humming noise? How could the humming noise be related to a leak anyway?
2) Concerning inhibitor does this break down over time and should I be asking my plumber add more in each year to preserve the levels in the system?

But if anything thanks for reading. It makes me feel better writing all this down at least.
 
are the trvs that are making the noises fitted to the hottest pipe eg when the system warms up that pipe should be the warmest out of the two on each rad ?

i would get it re dosed every 3-5 years unless you have a leak etc
 
are the trvs that are making the noises fitted to the hottest pipe eg when the system warms up that pipe should be the warmest out of the two on each rad ?

i would get it re dosed every 3-5 years unless you have a leak etc

Thank you for taking the time to read and reply.

The TRVs are all on the right side of the radiator which is the warmest out of the two but not by very much.
 
I would ask your engineer to check the TRV's are all on the flow side of the radiators and if not to check if they are bi-directional. They may need swapping round if not bi-directional. Also have him 're balance the whole system again right from scratch and re-set and lock the auto-bypass. And check the pump speed setting if it is not an auto-vairible type. Good luck.
 
This is classic trvs put on wrong end. Dark brown water is indicative of an ongoing
issue with fresh airiated water being introduced, black occurs in a closed system
I know this because in my last house I experimented with this ...I used a clear bowl
micromag mag filter so I could see the difference. It did not matter as that house was sold for demolition recently. The set up was in a workshop where the boiler etc was sited . I suggest try the trv route first and knock the issues off one by one...but as its only 4 years surely the guarantee will hold. centralheatking
 
Thank you all for taking the time to read and respond. It's fantastic to read people's analysis.

The TRVs are bi-directional judging by the two directional arrows on the pipework. I do have access to the Baxi Boiler manual and I don't think this model (Duto-tec 2 Combi 33 GA) has a pump speed setting. I will try the re-balancing and ABV re-lock with a plumber to see if that helps.
 
just because they are bi-directional doesnt mean they cant go faulty when set at number 3 when almost closed the valve can be forced by the pump this is called catering. and you would need to find the faulty trv and replace
 
Sounds like the trvs shut down and open the abv under the boiler making a noise? If so adjust down the abv as long as one rad does not have a trv job done. If they all have trvs take the head off the bathroom one.
 

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