radiator valves thud when they come on

[dave1955]

My central heating system sounds like a firework display when the radiators come on. Each radiator takes it in turn to "thud". Does anyone know why?
This has been going on for while now and today 2 rads started leaking. Is there a link do you think?

 

[Andygasman2010]

Sounds like your TRV's are one-way flow. They may need refitting on the other side of the rad. Is this a new fault? Have you had any work done on the heating system recently?

 

[dave1955]

No, the system has worked fine for about 7 years but the fault seems to be getting worse over the last 2 years. Tthey are the same TRVs as when we moved in 9 years ago. It was a new build at the time.
The only work done was to have the boiler serviced, but we have used the same guy every year.

 

[Andygasman2010]

Have a close look at the metal body on each TRV, see if you can see an arrow. The arrow should point to the direction of flow.

 

[dave1955]

Yes, I can see an arrow pointing in the direction of flow, but how do I know which way the flow is going? Do I turn on the rad and feel which end gets hot first? The leaking end is the lockshield end, but it seems to be OK when the rad is off1

 

[Servotech]

Stick some Fernox in the system that should sort it out.

 

[Andygasman2010]

Flow goes hot ---> cold the end that gets hot first is the flow into the rad, the arrow should point this way

 

[dave1955]

I have checked out the system, over half the radiators are fitted the wrong way! How serious is this likely to be?
Would it be easiest to replace the wrongly fitted TRVs with 2 way TRVs?

 

[Andygasman2010]

You could swap them side to side which would cost nothing but it'd be twice as much work as just fitting two-way ones.

 

[Servotech]

I have checked out the system, over half the radiators are fitted the wrong way! How serious is this likely to be?
Would it be easiest to replace the wrongly fitted TRVs with 2 way TRVs?

I would give some thought to replacing all the TRVs with manual wheel valves (much better and you are then in full control) all are multi directional.
Then just add some fernox as you refil I'm sure that will sort out all the problems.
Jobs a good un' (as they say).

 

[Andygasman2010]

I have checked out the system, over half the radiators are fitted the wrong way! How serious is this likely to be?
Would it be easiest to replace the wrongly fitted TRVs with 2 way TRVs?

I would give some thought to replacing all the TRVs with manual wheel valves (much better and you are then in full control) all are multi directional.
Then just add some fernox as you refil I'm sure that will sort out all the problems.
Jobs a good un' (as they say).

But he'll lose temperature control with manual valves...