One Pipe System

[cornishgas]

Hi all, fitted a new rad on the ground floor of a small house with a worser bodge combi. Pipe work running from the room above. There was already a loose board upstairs which I lifted and teed into "flow & return", filled up and everything was pretty as a picture until I fired her up... No heat in rad. To cut a long story short, I lifted more boards until I discovered I'd teed into the branches to the upstairs rad off a one pipe system. So I teed into the main run, no improvement; built an injector tee with a 15-22 reducer, slightly warm. Ran out of time & need to go back. I was thinking I might run the flow into the top of the rad (both valves currently at the bottom). Does anyone have any bright ideas?

 

[PrenticeBoyofDerry]

On a one pipe system it is important that the radiator sizes and location are correct, starting with smaller rads at the start of the circuit and the larger ones at the end. Radiators must be as close to the circuit pipe as possible, teeing off for long lengths is not suitable and the radiators will not function. So I would at least extend the integrity ring of the circuit, to prevent cold rads, or at best update it a two pipe system.

 

[simond]

I think the critical piece of information from the OP is the fact that they seem to have fed the radiator from the room above.

A radiator on a one pipe system will not function if it is physically below the 'one pipe', because there is no gravity circulation possible.

Whether you have big rads at the start and little rads at the end is irrelevant to this query, that is just to help minimise the effects of the small temperature gradient in the pipe.

 

[cornishgas]

Converting to two pipe is last case scenario. The feed to the downstairs rad comes down the corner of the room in 15mm. So if I replace that by extending the one pipe down that corner in 22mm (same as existing one pipe) and loop back up then tee off to the new rad from that, which will be about a metre from it allowing for gravity to help as best I can then it might be a winner.

 

[Agile]

There are several ways to fit one pipe systems.

The traditional way is to run a pipe underneath and let that feed by mostly gravity upwards into the rad.

But its also possible to mostly feed it through the rad with a bypass pipe with an adjusting valve. That way will allow a feed to the downstairs.

Not the best way perhaps but it will work.

A 15 mm one pipe was very common in small cheap houses in the Midlands and it sometimes needs a high head pump to obtain enough flow through it.

Tony

 

[cornishgas]

Thanks Agile, I'll try that way first, sounds a lot easier!

This seems to be installed the traditional way but it's getting pumped from a newish combi!

 

[simond]

The bypass method is a bodge, there are a number of reasons why technically this is very much sub optimal.

However this is a DIY forum, I'm just surprised at some of the advice given out by one of the top ten domestic gas technicians in the UK.

By his own reckoning.

 

[cornishgas]

The bypass method is a bodge.

OK Simond, I'm not DIY but looking for advice on a system that I don't have a huge amount of experience of, very rarely come across it down here, infact asked my old boss about it and he said he'd never come across one (although he has only ever worked in about a five-mile radius and installed most of what he now works on!). If I had recognised that it was a one-pipe from the start then I wouldn't have got to where I am. There was no visible evidence that it was like this untill I'd pulled up half the bedroom floor. It's not even an old house, I'd guess about 25 year-old terraced in a housing estate.

So...are you saying that I should do as I said in the post before last? Or should I run the one-pipe loop all the way under the rad and back?

 

[Agile]

Come on Simon list all the disadvantages in doing that to achieve the required solution.

There is only one that I can think of.

Since Cornish has got into a bit of a problem then I am suggesting a solution to him which will work.

So what is Simon's preferred solution other than totally repiping it within the "fit one rad" price he has quoted? £90 materials and a day's work!

Tony

 

[cornishgas]

BTW, that 5-mile radius is pretty much true and it's a semi-circle as he lives on the coast!