Radiator problem

WageSlave_3

Hi,

I have a persistent problem with one of my radiators in that I have to bleed it three times a week as it is half empty. It is the only one affected in such a way. I have checked around the radiator and under the floor and there is no sign of a leak. I have heard that it is possible for air to enter the system and I suspect the point of entry must be between the radiator and the hot water supply (I can’t imagine it is the exit pipe. I was wondering if anyone might have any ideas on how I might resolve the problem? My thinking is to use epoxy resin to seal any joints to stop air entering, but I may be well off the mark. Any ideas would be really appreciated.

Thanks in advance!
WS

PS: Yes, I know, I have just submitted THREE questions in a row on new threads. Thought it easier to keep these all seperate. :rotfl:

moneysavingplumber

It will depend very much on the system design. If you have a conventional indirect, gravity fed system incorporating the cylinder, then often air intake is caused by the cold feed/vent arrangement in relation to siting of the header f & e tank and the pump, and may be exacerbated by resultant blockages and sludge, especially in and around the pump and the feed/vent point. Air=sludge and sludge=air I'm afraid. Is the radiator situated at a high point in the system, within a loft conversion by any chance?

If you have a more modern sealed system then check the pressure relief valve discharge point, usually a piece of 15mm pipe kicked in to the wall at a low point on the outside of the building, to ensure it isn't dripping.

refundable99

It might be that air is being drawn in through one of the radiator valve spindles. Check round the tops of the valves under the knob/wheel when the pump is OFF. Any sign of water then would indicate that is where the air might be entering the system when the pump is running. Best to check after the pump has been off for some while.

bockster

air could be getting in at any point on the system but may always show up on one particular radiator. this sounds like a big leak though and would expect to see water escaping when pump off. i favour one of two things.

1, is the system sucking the header tank dry which is what i think moneysaving plumber is getting at, obviousy not if its a sealed system.

or

2, is the boiler noisy when on? could be 'kettling', the boiler overheats the water, possibly due to low flow or contamination, this, i'm told, can creat gas in the system ( is the h in h2o hydrogen?) i'm also told you can check this by trying to ignite the gas when bleeding the rad:eek: .

i've never had profesional confirmation of this, i'd love to here what some of the plumbers on here think of this theory......

anyway hope this helps.

WageSlave_3

Thanks, guys.

The system is indeed a conventional gravity fed system. I have checked the feed cylider and it is full and clean. The radiators are all on one level, so no upstairs, downstairs issues.

What I didn't add was that I had drained the system 5 weeks ago to move one radiator feed and swap the radiator for a smaller one (needed to do so after some building work), so I know it wasn't a dodgy radiator. I checked then for leaks under the floor as I also replaced a broken floor board near the main manifold (by co-incidence) and didn't see any. I have not checked since.

I have just bled it again and held a lighter to the bleed value. It didn't ignite but I did notice the flame was being drawn into the value and not was not blown away from the value! That has really confused me. The radiator did fill and I shut it off when it started to splutter and drip.

Sludge is a real probability. When I have removed radiators in the past, there has always been quite a bit and I doubt the system has ever been cleaned. I am now wondering if I should buy some chemical desludger, drain the system, add it, let it run for 4 weeks (as per the instructions) and drain again before refilling with anti-corrosion chemical added (which I did add 5 weeks ago)?

Finally, I will check all the spindles, around the pump (which is where I hear air can be drawn in) and around the manifold under the floor.

It's not a major problem and I did note it took a lot less time to bleed than the last time. Still, it's an annoyance and I suspect it means I use more fuel to run it with this issue.

WS