Downstairs radiators not heating even though hot water is getting to them

[YellowJoe]

Hi there

Our 3 bed house had an issue with a diverter valve 3 weeks ago and since getting it replaced 4 of the 5 downstairs radiators are not heating up (2 get a tiny amount of heat, 2 not at all). Upstairs radiators are fine, and the 1 downstairs nearest the boiler is fine too. Pressure is around 2, all radiators bled, and the pump is turned up to 3 and definitely turning.

Today a friend and I even took off all 4 of the non-working radiators and blasted out an impressive amount of sludge using a hose pipe. Gutted to say even this didn't help.

Oddest thing is that the white pipes leading from the walls to the radiator are getting hot on most of the radiators, so no idea why the hot water isn't getting in (they are all open on both sides...).

I'm pretty much at the end of my tether (thanks mainly to the wife's moaning...) so any suggestions would be brilliant. I've spent most of the last week reading this forum but can't find a problem quite like this one. It's a good puzzle at least....

 

[ShaunCorbs]

When you removed the rads did you test your getting water from each of the pipes ?

 

[YellowJoe]

Not really. Would have been sensible I guess!

They did all fill up easily enough afterwards though. Also, sprung a leak on one earlier and water came from both pipes on either side....

 

[ShaunCorbs]

They could have a blockage best to test each pipe if your getting flow from both it should work but if your not there's your problem

 

[YellowJoe]

Thanks Shaun, will give it a crack.

Was thinking that with some much sludge in the radiators it's likely there's going to be a decent amount in the pipes too. What's the best way to clear that out? Power flush? Was considering a cheap (non-chemical) option of pushing the pressure up to 3+ but I imagine that's dangerous and unlikely to work?

 

[ShaunCorbs]

I would see if you have water from both the pipes first no point in getting too far ahead

And other than pushing the pressure upto 2.5 bar nothing, best get a pro in if it doesn't work

 

[YellowJoe]

Thanks Shaun. Last question - should the 2 pipes going in/out both be hot, or just 1? I'm gonna struggle to detach the radiators and check them fully for a few days.

 

[ShaunCorbs]

One should be hot enough that you can hold your hand on it for long the other one should be cooler than the hotter one

 

[YellowJoe]

Ok thanks

 

[FunkyOstrich]

Have you balanced the system at all or changed or fiddled with some of the valves on the radiators?

 

[king of pipes]

Turn off all the rad valves on the radiators except one and let the heating run the pump should push any air out do this one by one until they all have been hot then open em all up and try it again . cheers kop

 

[YellowJoe]

Thanks lads have tried balancing previously using this video but will try again doing what KOP says. Is there any particular order I should be trying to get the non-working radiators to work, or does it make no difference?

 

[king of pipes]

Try the furthest one from the boiler first

 

[Old Account]

As above really, like @king of pipes has mentioned.

 

[YellowJoe]

Cheers guys. Just closed all the rad valves except one radiator, but no joy. It's getting maybe 5% warm (i.e. you can just about tell it's not totally cold). The pipe going in is pretty warm, but the radiator itself is doing nothing really.

I'll try a few other ones, but if that fails, best logic I've got is that there's some crap in the out pipes so will try to put some cleaning chemicals through the system I reckon.

 

[FunkyOstrich]

by the way, when balancing you must take off all the thermostatic valve heads. Also, check if the small pin under the head moves freely. They sometimes need persuading. Take a pair of pliers and move it up and down. Open the rads that don't get hot all the way. So to recap, thermostatic head off and all the other valves all the way open. I hope that helps!

 

[YellowJoe]

Thanks @FunkyOstrich . We only have thermostatic valve heads upstairs (where the radiators are working). Do I still need to take these off for balancing? I've turned them all to 0 already. The ones downstairs are more old school, but I've opened and them with pliers no probs.

 

[Vee]

Know it sounds daft, but did you check the pump valves are fully open? Likely one might have been turned off for diverter valve change now restricting flow?

 

[king of pipes]

It's your pump then get it replaced bud it's the heart of the system they wear out and get lazy you can spend hour messing around if it won't push through one rad downstairs then its failing to produce the head needed get it swapped . Cheers kop

 

[YellowJoe]

Cheers. Was thinking about that @king of pipes . How much does a pump change normally cost, and is it a job I can do myself? Pump is a Bosch Thermotechnik.

Before I do that, which pump valves do you mean @Vee ? How many in/out are there? Seems unlikely as the hot water is fine, but always a chance I guess!

 

[king of pipes]

£100 for a decent pump joe easy enough to change yourself providing your valves hold either side of the pump . cheers kop

 

[YellowJoe]

Cheers.

 

[Vee]

Pump valves are the brass pieces, fitted to both sides of the pump you see above with either a screwdriver slot to turn or a square spindle end to put a spanner onto.

 

[YellowJoe]

Thanks Vee will check it out.

 

[YellowJoe]

Just coming back to close this one off.

Turned out we had pretty hefty blockages in the return pipes of 4 of the downstairs radiators. We diagnosed this by trying to do a homemade flush using hosepipes connected to the mains, then to a flow/return, then out of another flow/return, then into a drain. Nothing could get through these pipes.

Managed to fix it using a combination of a foot pump, Sentinel x800, and hard work. The foot pump was the key. Managed to break down the blockages after many hours of trying. Got pressure to over 12 bar when the system finally coughed out a whole load of black sludge (RIP our carpet), mainly filled with little black bits of metal.

All working now. Thanks to all advice and assistance from this forum. Much appreciated.