"Blocked" System

[WhereInSussex]

Hi,

I recently purchased a house, heating system "needs attention" was in the particulars. When we looked around, the pipes in the airing cupboard were warm and the boiler was running, so we thought it was probably just the valve or something.

Fast forward to last week when we completed and when the heating system was switched on from cold the boiler ran for a couple of minutes the pipe coming out got too hot to hold and then the boiler stopped. After a few minutes of cooling it would run again and after about an hour the pipes around the pump would begin to become warm. After a few hours we can get luke warm water (probably around 40°C) out of the taps but the radiators never heat (although water can be heard flowing through them).

I have "Home Emergency" cover from my bank, so called them out and after 45 mins of poking about, sticking a magnet to the copper pipe just below the pump, taking some water samples and not going in the loft (because there is nowhere to lean ladder against and it's not boarded!) the diagnosis was "your pipes are blocked and if it was my house I'd replace the boiler and pipework", took lots of photos with an iPhone and went away again saying something about "they'll be in touch".

A friend of mine suggested that getting a reputable local plumber to do a power flush may be the solution here (rather than replumbing the house) but he's no more of a plumber than I am an astronaut.

For reference the water temp leaving the boiler is 74C, return is 30C after running on continuous all day, the divert valve operates correctly and I took big screw out pump and it was going around (and some water came out). When I opened the bleed valves above the divert valve, there was no air, just a trickle of water. The samples of water taken were "reasonably clear with some chunks in" as the engineer said on the phone to his office this PM.

Does anyone have any thoughts on this? Does it sound like a power flush will be successful?

 

[ukgas]

Pop up into the loft. Check the F&E tank (smaller tank) has water in and that the ball valve isn't sticking. If the tank is full it could be a blocked cold feed. Simple enough fix for a heating engineer, just involves cutting out a section of pipe work and replacing. A power flush will not cure a blocked cold feed.

 

[WhereInSussex]

Thanks UKGAS, I'll get in touch with somebody ASAP after a trip into the loft tomorrow. As the immersion doesn't work either (I guess they burnt it out because the gas hot water didn't work) I really need to get this sorted as we're moving in on Monday!

 

[Armo74]

What speed is the pump set at?
If you go in the loft when the heating is on does water come out the vent pipe?(the u shaped one going back into the small tank).
Do your radiators have thermostatic valves on them?
Does the small tank overflow down the warning pipe?

 

[WhereInSussex]

What speed is the pump set at?
If you go in the loft when the heating is on does water come out the vent pipe?(the u shaped one going back into the small tank).
Do your radiators have thermostatic valves on them?
Does the small tank overflow down the warning pipe?

The pump is set to 3, the radiators aren't thermostatic and are "on" and I haven't been into the loft yet

 

[Armo74]

If there is no blockage the pump has probably had it if the samples came back pretty clear.

 

[ukgas]

If there is no blockage the pump has probably had it if the samples came back pretty clear.

Even with a failed pump the top rads would still get a bit of heat. My money's on a blocked cold feed.

 

[WhereInSussex]

The pump was his first suggestion, but then he seemed to think it wasn't that because it appeared to be running and because a magnet stuck to the pipe.

I have just been recommended a local plumber, so will give him a ring tomorrow after I've had a look in the loft.

 

[ukgas]

Magnet will be sticking to the iron oxide blocking the pipe. Blocked cold feed for sure. Nice simple fix shouldn't be to expensive.

 

[gigz]

Get a price to fit a magnaclean or similar while he's there.

 

[DP]

ukgas, if the cold feed is blocked, surely there will be SOME water in the system to heat rads at a lower level.

Rest assured pipes need not be blocked, but issue within the boiler could also lead to similar scenario

Powerflush will do diddly squat if pipes are clear- what is needed is proper checks instead of 'sticking finger in mouth and checking wind direction'

 

[ukgas]

ukgas, if the cold feed is blocked, surely there will be SOME water in the system to heat rads at a lower level.

Rest assured pipes need not be blocked, but issue within the boiler could also lead to similar scenario

Powerflush will do diddly squat if pipes are clear- what is needed is proper checks instead of 'sticking finger in mouth and checking wind direction'

OP mentioned the flow was to hot to touch, boiler is overheating due to lack of circulation. No problems with the boiler. Either pump, motorised valve or a blockage. Previous plumber to attend ruled out pump, and I'm assuming motorised valve. He also mentioned a magnet stuck to pipe work. Blocked cold feed with enough crap in it will stop circulation. Seen it countless times

 

[DP]

Went to a Gloworm (cast iron HE) a while ago where the flow would get hot and then burner would shut down. End result same a OP is having. Blockage in boiler as only half the heat exchanger was functioning and the stat phial was in the blocked section. Cleared the blockage and all functioned OK after that.

sticking a magnet to the copper pipe just below the pump

Does not say the magnet stuck to the pipe.

He also said the water was clear.

 

[WhereInSussex]

Thanks for all the suggestions, will be phoning a plumber (or two) later.

The magnet stuck to one area, I think it was around a junction just below the pump (but may be wrong).

 

[ukgas]

A possibility DP. Hard to judge without seeing the system. From the limited info we have my money is still on a blocked cold feed. Off Topic, are you the infamous mr puller from the old screw fix forums?

WhereInSussex hope you get it sorted, could you please update us on the cause when it's rectified?