Apparent blockage in CH circuit - locating problem

[jm9431]

I have cold radiators downstairs, but hot ones upstairs. The feed pipe splits 2 ways a metre outside the boiler and the upward leg is hot but the downward leg isn't. When the boiler fires the downstairs leg does heat, but that is probably just the pipework. As the nearest radiator is lower than the boiler and only a few metres away that raditor does warm a bit, but the outlet of that radiator is cold and the inlet to all the other downstairs rads is cold too.

I have had the system power flushed but this hasn't helped. I have also had the boiler checked and there is no problem with the pump. The flushing should have cleared a blockage but it looks like my last resort is lifting floorboards - although I really don't want to do this. My obivously less than brilliant plumber then said he has no clue and "feel free to get somebidy else to have a look at it".

My question initially is how best to locate a blockage in hidden pipework with minimum distruption.

 

[cross thread]

most blockages are at tee joints a check is to run a magnet over the pipework if it is attracted you have a build up and gives an indication on where to start

 

[bathjobby]

If all on that loop are cold, then presumably any blockage is between the boiler and the first rad off the loop.

 

[jm9431]

If all on that loop are cold, then presumably any blockage is between the boiler and the first rad off the loop.

I have also come to that conclusion, but is it not possible that the pipe between 2 radiators is blocked?

 

[bathjobby]

Sounds like your ignoring the logistics of the situation because its easier to access somewhere else ?
My wife once dropped her house keys walking home one night. She knew she hadn't dropped them under the only street light on the route, but continued to look there as it was the only place she could see anything

 

[jm9431]

Sounds like your ignoring the logistics of the situation because its easier to access somewhere else ?
My wife once dropped her house keys walking home one night. She knew she hadn't dropped them under the only street light on the route, but continued to look there as it was the only place she could see anything

What do you mean by that? You suggested that it was probably in one place and I suggested it could be somewhere else as well - in a far harder to find place.

I don't understand your comment

 

[jm9431]

It could also equally be between the last radiators and the boiler as no return = no flow just as much as no feed = no flow

 

[cross thread]

JUST TEST THE TEE WITH THE MAGNET THEN LOOK FOR THE KEYS!

 

[jm9431]

JUST TEST THE TEE WITH THE MAGNET THEN LOOK FOR THE KEYS!

Yes, I think I'll start with your advice and then move on to something else...

Thanks for your help and hopefully it works when I get home

 

[ChrisR]

You may not have a blockage, could just be an extreme balancing problem.
First try turning off all the upstairs rads and put the hw OFF. Then what gets hot?

 

[Agile]

Next when the downstairs ones are hot, turn on the lockshields upstairs by only ONE quarter of a turn and they will all be hot up and down!!!

How do people get paid for power flushing when they have not solved the original problem??? I would not have the cheek to even ask!

Tony

 

[doitall]

First thing you should tell us the size of the pipes going up and down.

Then you need to tell us what type of system you have fully pumped, sealed or whatever.

The problem will almost certainly be air related and a piece of cake to move with a hose pipe.

Turn all the rads upstairs off both valves, then remove the nearest rad to the boiler and connect a hose pipe to the return tapping and open the valve, keeping the system pressure at 2bar if possible. when the water flows without air for several minutes do the same with the flow pipe

The boiler must be electrically issolated as you don't want it coming on