Single Pipe Central Heating blockage

[davidf]

My mother-in-law has a single pipe central heating system. The boiler is working fine. Some of the radiators no longer get hot. All of the radiators have been removed and cleaned but the problem still remains. It is almost certain there is a blockage in the pipe. What is the best way to remove a blockage of this type. Thanks for your help

 

[hammers4spanner]

power flush your system

 

[dontknowitall]

Might be the pump needs changing. Are the upstairs rads warm and downstairs ones cold?

 

[Ermintrude]

Has the system been extended or rads changed perchance?

 

[Billy Bob Bob]

rip it out and fit 2 pipe 1 pipe never works and was a compromise

 

[Ermintrude]

rip it out and fit 2 pipe 1 pipe never works and was a compromise

it never works? Never worked for past 35 years or more? One pipers are fine! Just needs a gentle touch. Some people can't afford two piper. I would rater a one pipe than micro bore or 10mm plastic .

 

[Ermintrude]

it never works? Never worked for past 35 years or more? One pipers are fine! Just needs a gentle touch. Some people can't afford two piper. I would rater a one pipe than micro bore or 10mm plastic .

how do some of the rads work? Is it on same circuit? If so its the legs not main run, unless u have altered pipework?

 

[RoryD]

Think it would be "nicer" if people put cogent argument rather than being sarcastic it just drives people away and gains absolutely F.A.!!

 

[Howsie]

Think it would be "nicer" if people put cogent argument rather than being sarcastic it just drives people away and gains absolutely F.A.!!

Guilty as charged (not in this thread but others). Thank you.

 

[davidf]

No, one downstairs radiator in the hall and 2 upstairs are working. The boiler is in the kitchen, along with the pump. I do not know the route the pipes take. 2 plumbers have suggested the boiler and pump are OK but have not been able to fix the problem. If it was the pump would you expect the rads nearest the boiler to be the hottest?

 

[davidf]

No, nothing has changed been changed. The rads all used to be piping hot.

 

[davidf]

My question precisely. I am presuming its all on the same circuit. Unfortunately I cannot tell, as I do not have easy access to the pipework. I find it hard to understand how several legs could become blocked. No pipework has been altered.

 

[Centralheatking]

Well said Ermintrude I agree with your comments and am also old enough to have fitted the system. If this system is slowing down then it might be pump or a blockage.

1st I would shoot it up with mains water pressure. Connect hose to drain point open drain and turn mains on, go round turning rads on and off BUT get someone else to watchover the over flow from the F & E tank incase it overflows - then just turn off mains shoot up for 5 mins, drain down back thro mains feed hose (outside tap makes this easy) and repeat untill the black and brown sludge is clear -

2nd put existing pump on fast then change pump . centralheatking

it never works? Never worked for past 35 years or more? One pipers are fine! Just needs a gentle touch. Some people can't afford two piper. I would rater a one pipe than micro bore or 10mm plastic .

 

[Centralheatking]

Why is there not a 'dont like' click point

I have fitted -years ago many sgl pipe systems
which were perfect & some i still look after & still work. They also are cheaper in terms of materials/labour etc but I have not fitted one since June 1983 in Beckhamton Ave Bath(still got my records !!! centralheatking

rip it out and fit 2 pipe 1 pipe never works and was a compromise

 

[SafeGasInstall]

have you checked the valves are working ok ?
have you rebalance the system after you or who ever had rads off to wash them ?

 

[Ermintrude]

U could take off valves one by one and make a bridge peice , basically 15mm push fit pipe with two compression elbows on ends, if bridge pipe heats and other rads come on then u know the partial blockage is between the two legs u just Bridged. ( possible but not really plausible that mutipul legs are blocked) system may be filled with muck or perhaps pump needs a jigger. I have about 20,0000000 pumps if u want a second hand one for cost of postage just pm.

 

[davidf]

THanks for the advice. She had a plumber come round who took off and cleaned all of the upstairs rads. He also opened the valve on each leg to allow water to come out and put the rads back. But still only the same rads got warm. I don't believe they are the rads closest to the boiler. But the rads he ahd cleaned out did not get warm. It is as primatic system with no header tank, so we can't use inhibitor and the plumber said he could not power flush it.

If the pump was at failing would you expect the rads nearest the boiler to be the warmest?

Also to make matters worse the idiot who fitted the pump has jammed it in the gap betwen the wall and the side of the boiler and the isolation valves for the pump no longer work. THe plumber has suggested changing the head of the pump. Is this a good next step?

 

[davidf]

THanks for your help. I might take you up on the offer of a pump. I need to check the make and model. It will be quite a hard job to replace it as the pump is jammed between the wall and the side of the boiler and the isolation valves don't work any more. THe plumber suggested changiing the head of the pump. Is that a good approach?

 

[Ermintrude]

Yeh the head does the work so change away 4mm or 6 mm hex driver, dont know size just know how it looks. Has it always been like this? Lift up floor boards, is the one pipe as close to rad as possible, (legs go straight down ) max 400mm long? Don't worry about inhibitor or additives . Marmite is fine for rads. Fit a Magna clean in return if ur really bothered. I'm still betting on obstruction . It could be between legs on rad that's getting hot. U can hire a thermal imaging camera for about £35. Soon show up problems.

Water flowing out valve due to gravity is completely different to flowing through when pumped.

 

[Billy Bob Bob]

Why is there not a 'dont like' click point

I have fitted -years ago many sgl pipe systems
which were perfect & some i still look after & still work. They also are cheaper in terms of materials/labour etc but I have not fitted one since June 1983 in Beckhamton Ave Bath(still got my records !!! centralheatking

it does not work as well as 2 pipe if it did we still be fitting it you are talking nonsense man one pipe was a pioneering effort and quite frankly totally useless

 

[Mike Jackson]

it does not work as well as 2 pipe if it did we still be fitting it you are talking nonsense man one pipe was a pioneering effort and quite frankly totally useless

Nothing wrong with a correctly installed one pipe system. I've fitted loads in the past and plenty are still working perfectly. Main problem is a lack of understanding of how they work when people make alterations. The main issue with them is they are not as energy efficient as a two pipe system when used with a condensing boiler due to the higher return temperature.

Blockages in the main circuit are rare because there is always a good flow round it. Blockages are normally in the individual legs to the radiators. Another issue I've come across is when people change pumps and set the speed too high on the pump. The radiators rely on gravity convection from the main circuit. If the pump is set too high the water rushing around the circuit doesn't allow time for this to take place and the radiators don't reach temperature.

 

[DirksPlumbing]

Nothing wrong with a correctly installed one pipe system.

Please look at the next quote.

The main issue with them is they are not as energy efficient as a two pipe system when used with a condensing boiler due to the higher return temperature.

Overall your post was on the spot. But even on conventional boilers I have seen a 10-15% drop in gas usage by converting the system to two pipe. Plus the usual "Wow, I never had such a good heating".

Nobody has asked if there had been possibly 3 way valves fitted? I am assuming the 3 way ones are not all that popular.

OP: the valves on the radiator are both bottom entry? there is no bridge (pipe) aside the radiator?

I personally find single pipe systems technically fascinating but completely impractical. But microbore is no much better. How often do I come across >2kW rads dangling on huge runs of 8mm?! And not even a horse shoe attached to it.

 

[Sparkgap]

Single pipe systems rely on gravity circulation through the rad, plus a slight amount of pressure differential between flow and return. If the pump speed is turned up and water belts through pipe there will be a greater pressure drop per length so a bit more circulation through the rad due to PD, depends on the design. Modern rads though tend to have higher resistance with the type of connections. Plus you can't get Armstrong diverter tees any more and have to do stab-ins! One method I've used is to drop a pipe size between F&R connections on the rad which helps.
Problem with SP systems is the drop in mean temp through rads as you go down the circuit, so rads towards the end of the circuit have to be larger.