Single pipe central heating advice

[james7777777]

Hi,

I have a single pipe loop central heating system and have issues with some radiators not getting hot at all. I have tried changing the valves, radiators, flushing the system etc and the problem must be related to the pipework and / or balancing i think. The flow pipe on the radiators is getting really hot but the water is not flowing through the radiator as the outlet pipe is cold. I have heard that on a single pipe systems the radiators must be close the main feed pipe - in my case they are about 2-3 metres off the main pipe.

I need some advice - is there anything i can try to improve the radiators other than replumbing? (there is a recently fitted wooden floor in the house so want to advoid this!).

Is it common for poeple to replace single loop systems with a feed and return system and what is the typical cost for a 5 bedroom house?

James

 

[Gray0689]

Hi,

I have a single pipe loop central heating system and have issues with some radiators not getting hot at all. I have tried changing the valves, radiators, flushing the system etc and the problem must be related to the pipework and / or balancing i think. The flow pipe on the radiators is getting really hot but the water is not flowing through the radiator as the outlet pipe is cold. I have heard that on a single pipe systems the radiators must be close the main feed pipe - in my case they are about 2-3 metres off the main pipe.

I need some advice - is there anything i can try to improve the radiators other than replumbing? (there is a recently fitted wooden floor in the house so want to advoid this!).

Is it common for poeple to replace single loop systems with a feed and return system and what is the typical cost for a 5 bedroom house?

James

Yes Its typical to change one pipe systems are not good and price for a 5 bed house I'm afriad the only persons that can tell you is the plumber you get in to give you a price we can't guess on jobs like that but it will be a lot of work I'm afraid

 

[doitmyself]

A well designed and adjusted single pipe system is just as good as a two pipe system - they are still used in commercial installations. Unfortunately domestic installations were installed on the basis of cheapness, so design and adjustment was a minor consideration.

As Gray says, changing to two pipe would probably be sensible, but you should get several quotes for the work.

 

[GasmanxxxR1]

Take off and manually flush the radiators.

When you said you flushed the system was this a powerflush or just a system flush with chemicals.

Powerflushes dont tend to do any good on one pipe sytems as it just bypasses the rads and does the pipe work. As you have said the pipes get red hot then this suggests that you have a flow restriction in the rads - sludge. Close the valves on both sides, carry rad into garden and flush with hose pipe. Job done

 

[james7777777]

Thanks all,

I have fitted new radiators so they are sludge free! I just dont think the single pipe system is coping with the far away radiators i have in an extension. I got a qoute today to change the plumbing from single loop - £1500 as long as i remove the flooring/carpet which seemed pretty good to me.

 

[Gray0689]

Thanks all,

I have fitted new radiators so they are sludge free! I just dont think the single pipe system is coping with the far away radiators i have in an extension. I got a qoute today to change the plumbing from single loop - £1500 as long as i remove the flooring/carpet which seemed pretty good to me.

Sounds a good price

 

[AlexGas]

I guess the installation is quite old.
Single pipe system is no good. I'd say rip it out. Change the lot, might as well, cos old fittings might play up later on.

 

[SafeGasInstall]

1.5k is this for materials only ?as if it's for materials and labour it looks too good to be true !!!! U looking of min 3k labour and materials for pro job !

 

[Gray0689]

1.5k is this for materials only ?as if it's for materials and labour it looks too good to be true !!!! U looking of min 3k labour and materials for pro job !

We can't see the job from here
So get a few quotes from good local plumbers

 

[jazz drummer]

have you had the pump checked out ! dont be too hasty with your cash

 

[tamz]

Thanks all,

I have fitted new radiators so they are sludge free! I just dont think the single pipe system is coping with the far away radiators i have in an extension. I got a qoute today to change the plumbing from single loop - £1500 as long as i remove the flooring/carpet which seemed pretty good to me.

Here may lie the problem. Did you fit new trv's when you did this?
One pipe systems need special low resistance trvs as the radiators actually heat by gravity (thermosyphon is the new word for gravity).
Std trvs will not work unless the main loop is directly below the rad and even then the rad will not heat properly.

 

[james7777777]

Yes we had a new pump fitted so it's not that. most of the radiators in the house get hot after a while except 3 that are the farthest away.

1500 includes parts but the old radiators are all staying. I think i am quite lucky as all the raditors seem to be "rspurred" of a loop that runs in thew hallways upstairs and downstairs so it is quite easy for the plumber to access. He wouls just need to cap the od loop and use that as the flow and add a new pipe for the return - about 2-3 days work for 2 people.

 

[james7777777]

oh..i didnt actualy fit TRV's but i did just use standard valves - could these cause an issue?

 

[james7777777]

As a final update I have now seen that the "Spurs" off the loop for the radiators not getting hot are only 5 inches away from each other - i have read they should be at least 1 metre apart to allow the water to flow into and out form the rad. Plus i have not fitted low resistance valves which i appear to need.

So i can either move the pipework and refit the valves on 3 radiators and stick with a single pipe system or pay £1500 and get the whole thing replaced and updated. Im thinking option 2 is the more sensible one.

 

[paulnwales]

single pipe systems have to be balanced poperly or you have no hope of it working correctly. if you know how to balance it try that first.

 

[justlead1]

To give you a bit of time to save up to carry out the work. Totally out of order but using say mole grips squeeze the 3/4" / 22 mm between the branches to the rad. This increases the frictional resistance on the main circuit, pushing more through the rad. So i have heard.

 

[tackleburger]

1.5k is this for materials only ?as if it's for materials and labour it looks too good to be true !!!! U looking of min 3k labour and materials for pro job !

I don't know, I have a good second year apprentice he and i can remove and replace a system with a combi and say 6 or seven radiators in a day plus maybe a few hours next day snagging. A new install from scratch can be done in a day easy if we can get an out of work apprentice to lend a hand. So a re-pipe no boiler to fit is a days work for us plus say £600 max on materials I'd say £1500 is about right for two blokes a van all that pipe and fittings, lagging inhibitor etc with the VAT.

Where on earth do you get 3k From even taking a week to do the job you'd have a cheek.

 

[SafeGasInstall]

new install can be done easy in a day in CANCEL property I stopped the cancel work last year ,try do it in a nice home with 5 bedrooms with furniture in and nice carpets dawn and extention ,

where on earth you get the idea to comment my post like this

 

[altom]

I have a similar problem. I have a single pipe system and need to put a radiator in an ensuite some 4 meters from the one pipe loop. fitted the towel rail rad and was very dissapointed. Fitted one pipe tee'd off adjacent to the up pipe of the current bedroom rad and another piped tee'd adjacent for the return pipe of the same bedroom rad No water however was being pumped through the pipes although for 1 meter the out became very warm as if the pump was pushing the water along the pipe some whhat it. Just thought of an idea. Will a Check valve (non return valve) fitted in the return pipe help matters as then there will not be any pressure being forced back up the return pipe. thanks

 

[tamz]

One pipe systems circulate trough the radiators on gravity. The pump has very little effect. Teeing off the risers to the rad is the worst place to tee in. There are a couple of was to do this but unfortunately the knowledge is dying out and the ones who still know how are all too old to be bothered much.

 

[Deleted member 25704]

The cost of the suitable rad valves is often 5 times that of normal valves - they are also female, so need a 1/2 chrome male to 15mm copper - which adds to cost.

The lock shield valves will also need replacing - pegler belmonts - it could cost you £50 per rad just for cost of the pairs of valves for each radiator.

You are right about the distance between the pipes where they tee-off, and swept tees preferred for this.

The rads could also be unsuitable because of the high resistance -check manufacturer.

All in all, the re-pipe is the cost effective option here.

 

[warrington]

in one-pipe system, pump only forces water around the main circuit and not directly through the radiators. This means it is important TO SELECT RADIATORS that allow minimum resistance to the flow of water. And radiators on the system pass cooler water back into the circuit. This means that the radiators at the end of the system are cooler.
You said radiators are new, so i can say from what you explaining is radiators , so there is a resistance to the flow. My advice as they say to turn system in to 2 pipe.

 

[altom]

Re adding another radiator on a one pipe system. Thanks for above answers I now understand you can not do what I thought I could do!! However can I cut into the current radial one pipe circuit, cap the end pipes and extend the circuit to now include the new radiator. In otherwords the one pipe system goes under the floorboards and up to the new rad. At the new rad you would T into in inlet and make sure a bypass pipe is placed to join the return pipe. That is all you have done in reallity is to extend the circuit and pipework some 8 meters to that rad and back into the original circuit. I can not see a problem but I am not a heating engineer or a plumber. Have I got it right or am I barking up the wrong tree??

Thanks for any answers

 

[tamz]

That would work.

 

[WHPES]

Spending money on a single pipe system is a waste of money.