A microbore bore

[waterfool]

I have a microbore system with a 15 to 18 year old boiler running six rads........five are scalding and one, the largest and most distant only heats partially and the return is barely warm.........I have removed and flushed rad...balanced system....flushed the pipes from the manifold...switched the flow and return pipes under the floor with other rads to test and the situation remains the same....It has been suggested to me that the pump may be knackered (Probably the original)...how realistic is this given that the other rads are hot and how could I tell.....to the touch the pump vibrates gently...The boiler is a vailliant vcw with a grundfoss pump........I could sure use some helpful advice.........every night I'm coming home and taking my system to bits and its sort of ****ing me off.....help

 

[JohnD]

Have you balanced it (see FAQs)?

Then maybe a chemical clean and flush, then refill with inhibitor.

 

[Paul Barker]

I had this problem with one of those stupid systems that has one rad valve that takes both pipes. In the end I found that the worst thing you can do in such a case is fully open both flow and return to that rad as all that happens is all the flow does a U turn and goes straight back down the return. You actually have to turn down the return to get the water to hang around in the rad.

I would never ever fit such a craisy valve.

 

[tonygerm]

try turning of the other valves leaving the dogy one open ,if it still posists cheq the valves on it. ps what do i know im a decky

 

[chrishutt]

I had this problem with one of those stupid systems that has one rad valve that takes both pipes. In the end I found that the worst thing you can do in such a case is fully open both flow and return to that rad as all that happens is all the flow does a U turn and goes straight back down the return. You actually have to turn down the return to get the water to hang around in the rad.

The return insert inside the radiator must have been detached or corroded through to produce those symptoms. There's nothing wrong with the principle of the twin-entry valve, providing the insert is on the return.

 

[garethgas]

Sounds to me like a yorkshire twin entry valve.
I agree with Chris on this one, the inserts used to either drop off or corrode. If I remember correctly a short length of 10mm will give you a substitute.
garethgas

 

[Soggy_weetabix]

just put the spreader back on.

Dave