Blocked pipe?

[Thorthumb]

I posted a topic earlier today about a cold radiator in an outhouse. After ruling out an airlock, I drained down the radiator with the system cold. I then opened first the TRV, closed it and then opened the LSV to check adequate flow. The TRV had a good flow of water but the LSV end just had a trickle although if I put my thumb over the opened valve there was still good pressure. I guess this means that the return pipe (its the grey plastic type, small diameter) is partially blocked or kinked. In the house, the pipe disappears into concrete and in the outhouse emerges inside some boxing. Between the two is a block paved yard.

Clutching at straws really but has anybody got any ideas to relieve the blockage without having to lift the block paving?

 

[MickyP10]

I'm no plumber but I'd open up both valves in the outhouse, mebs shuts a couple of rads down near the take off in the house and see what happens. Unlikely to be a blockage - more a balance/air issue I would have thought.

 

[Thorthumb]

The point where the pipes to the outhouse are connected to the large diameter flow and return pipes is right under the boiler so they are closer to the boiler than any other rads. I can't think why this rad should suddenly stop working unless the pipe has got blocked/kinked somehow. Is my description of the flow from the LSV what you'd expect from a blockage or is it the type of flow you would normally expect?

 

[MickyP10]

Again no plumber but would think it unusual for a pipe to suddenly block. Did it 'block' after you did something? If it's that close to the pump and bothrad valves are open and it's free of air, I would expect it to be hotter than a Newmarket tip.

Anc closing off some other rads in the house should move an airlock.

 

[calorific]

How did you rule out an airlock?

 

[onabudget]

depending on the diameter of this "grey" plastic kinked return pipe you might depending on angles be able to push through either some thing bore flex pipe or some microbore and remake the connections or at the very best clean out any debris. If it's a low point it might have sediment trapped in there that's hardened over the summer months.

Or you could isolate that section and use an improvised powerflush with a house pipe.

 

[Thorthumb]

How did you rule out an airlock?

Hi calorific,

The flow and return small diameter plastic pipes are teed off the large diameter copper flow and return main pipes under the boiler. At this point they are about 6" to 8" above the concrete floor which they disappear into. From there to the outhouse the pipe run is only about ten foot until they emerge behind the radiator cabinet in the outhouse.

I thought that when I disconnected the valves at each end they were connected directly to the main flow and return (which is supplying the rest of the house ok) by a relatively short length of pipe. Opening the valves let water flow as described earlier, good flow from the TRV end and a trickle from the LSV end but with good pressure in that it wasn't easy to stop the flow by blocking the valve outlet with my thumb. I thought that if there was air trapped in either pipe it would be purged by opening the valves.

Do you think there it may still be an airlock if so how can I shift it?

 

[Thorthumb]

depending on the diameter of this "grey" plastic kinked return pipe you might depending on angles be able to push through either some thing bore flex pipe or some microbore and remake the connections or at the very best clean out any debris. If it's a low point it might have sediment trapped in there that's hardened over the summer months.

Or you could isolate that section and use an improvised powerflush with a house pipe.

Hi onabudget,

You've got a point there, these pipes are the absolute lowest point on the system as they dip away under the ground outside which makes them even lower than the pipes under the floorboards in the rest of the house. I wonder if there is a product that would shift hardened sludge?

 

[calorific]

Sealed or open system?

Could be an airlock, or indeed the valve itself might be partially blocked and preventing adequate flow.

 

[onabudget]

I had the same problem and that's what it was or rather a very low flow out compared to the pressure being pushed in. I tried various things to try and break it up.

In the end I keep the heating on by running a bypass in plastic out a window as a temp solution until I found a plastic narrow bore pipe I could use to keep pushing at the muck and then alternative blasts with a mains water supply, after a few days it moves and cleared it was all the crud that had come from the rads, if there are kinks it will be trapped near these.

Just becareful that whatever you poke or rod with is not sharp as you don't want to create a leak.

Otherwise get a professional power flushing company in, but I suspect it will be expensive. Good luck

 

[Thorthumb]

Sealed or open system?

Could be an airlock, or indeed the valve itself might be partially blocked and preventing adequate flow.

Hi calorific,

It is a sealed system. It isn't the valve though as I went so far as to remove the valve and the flow out was still a trickle.

 

[Thorthumb]

I had the same problem and that's what it was or rather a very low flow out compared to the pressure being pushed in. I tried various things to try and break it up.

In the end I keep the heating on by running a bypass in plastic out a window as a temp solution until I found a plastic narrow bore pipe I could use to keep pushing at the muck and then alternative blasts with a mains water supply, after a few days it moves and cleared it was all the crud that had come from the rads, if there are kinks it will be trapped near these.

Just becareful that whatever you poke or rod with is not sharp as you don't want to create a leak.

Otherwise get a professional power flushing company in, but I suspect it will be expensive. Good luck

Hi onabudget,

The pipe is really small diameter, not sure of the nominal sizes but I guess it will be less than 10mm bore. The only thing I can think of to poke down it might be some piano wire with a tight loop on the end so it won't puncture anything.

 

[calorific]

This subcircuit is connected to the main flow/return under the boiler. As such you might be able to drain down the system and disconnect it from the tees. Personally, if there is room, I'd fit a couple of isolator valves off these tee's so that I could isolate and remove it easily enough in the future if needs be, and still have the main house all nice and toasty

Anyway, after isolating it, you could easily enough use some hoses to the tails and flush it through with mains pressure bi-directionally to maximise effect.. You never know, it might do the trick

 

[Thorthumb]

Thanks for the replies. Looks like a job for next weekend to isolate and trying to flush/poke it into submission. Failing that I'll have to get me shovel out.

 

[onabudget]

depending on the curves I used a set of screwfix roads for threading cables they cost me 20 quid or so but I did not have a tight curve, they are fibreglass and can almost bend double without breaking you screw them together and they are about 5 or 6 mm maybe thinner, they are about 1 metre each and I put 6 or 7 together, taping over the end with some gaffer tape to protect the pipe. Be careful you only rotate them the correct way otherwise you will end up losing them in there!, let me know you need any more details or you cannot find the rods in screwfix and I'll post a link but I think it's not allowed on here