hissing in radiators

[DrGonzo]

A few of the radiators around the house have a hissing sound/air sound in them. I turned a few down to 3 instead of 5 and that seems to stop it but sometimes it come back.

None of them are cold at the top, which would normally mean they needed bleeding so I am not sure what this is.

Sometimes the noise changes pitch but not that often.

Any ideas what I can do to solve this?

 

[Armo74]

Are the TRV's on the flow or return?

 

[DrGonzo]

Are the TRV's on the flow or return?

they are on the left hand side of the radiators as you look at it

 

[Diyisfun]

lol..that was funnny.

left or right wont help.
Feel the pipe what end gets hot 1st is the flow

 

[HERTS P&D]

If yours is on an open vent system, then turn your pump speed down.

Andy

 

[DrGonzo]

If yours is on an open vent system, then turn your pump speed down.

Andy

It's a Vaillant ecotec plus.
How can you turn the pump speed down? I turned the temp down but didn;t seem to do much.

 

[doitall]

Re-pipe the system with larger pipes.

Fit or adjust the auto by-pass.

Turn the lockshield valve off on the problem rads.

All the above.

 

[DrGonzo]

Re-pipe the system with larger pipes.

Fit or adjust the auto by-pass.

Turn the lockshield valve off on the problem rads.

All the above.

Landlord won't pay for any of that if there's a cheaper solution like turning the pump speed down but I don;t know how to do it.
All the rds make the sound so if the valve is turned off on all of them then they won't work?

 

[DrGonzo]

It's a Vaillant ecotec plus.
How can you turn the pump speed down? I turned the temp down but didn;t seem to do much.