Single to dual pipe system

[jasramsden]

Hi,

I have a single pipe system that I need to change to a twin as the upstairs rad just don't get anything at the far end of the house.

I am just in the process of ripping down the downstairs ceiling and wondered if it would be easier to do the following as the upstairs boards are 2 by 8 and lip under the plasterboard.

1. Can I just lay a new return pipe picking up each of the rads leaving the original as the flow? Do I need to connect the flow and return with a pressure value at the furthest point?

2. As I have the ceiling down, and the boards upstairs will be a nightmare to life, I am looking at feeding through flexible pipe (FloPlast from Screwfix). I would be to use copper but the job would be huge and this seems an good alternative.

Cheers,
Jason

 

[ALEC1]

Single pipe systems can work fine..assumng that the pipe layout is correct, the valves need to be high lift types...why all the drama?

 

[jasramsden]

Hi Alec,

The rads at the far end of the run never get hot, and since I have most of the down stairs ceiling down, I can see one run that goes round the side of the house (about 12m) until it gets to the master bedroom rad.

Also heard that F&R systems are a lot more efficient.

Radiators are original ( and seem tired ), but if I change them and there is now change, I'll kick my self for not changing the pipe work.

 

[CBF]

sounds like a good opertunaty to change it to a two pipe system which will work much better

 

[Terrywookfit]

Single pipe systems can work fine..assumng that the pipe layout is correct, the valves need to be high lift types...why all the drama?[/quote

It is my personal experience, that nearly all the one pipe systems that I have encountered in 40 years, are badly designed and installed even worse.
To make things worse, many have been added to and butchered from the original plan.

Changing to a two pipe system can only give positive results!!

 

[jasramsden]

Thanks Terry,

Is there any balancing required at all or can it the pipes just be chopped and re-routed (quickest way back of couse).

Do I need a pressure relief valve between the flow and return?

 

[Whitespirit66]

sounds like a good opertunaty to change it to a two pipe system which will work much better

Agree. If you can change to 2 pipe without too much disruption, it's worth it. No advantages to 1 pipe, but several drawbacks.

However one word of warning, if your system will then be part 1 pipe, part 2, this can sometimes make balancing difficult. How much of the system will remain as 1 pipe?

 

[jasramsden]

I'm planning to change upstairs first and then a month or so later will be changing downstairs.

 

[Whitespirit66]

I'm planning to change upstairs first and then a month or so later will be changing downstairs.

That will be fine. The downstairs heating may be a bit of a mare for the intervening month, but small price to pay.

When you mention 'pressure relief valve', do you mean auto bypass? What boiler/system/motorised valves do you have?

 

[jasramsden]

Yes, auto by pass sounds about right. Basically, what happens if all the radiators where turned off and the boiler was on?

It's a combi boiler and I have a mix of valves, most are thermostatic.

Also, what's your take on flexible pipe? It's going to be a nightmare pulling up the floor sheets so I can run the flexible pipe through the joists while I have the ceiling down.

 

[CBF]

just drill the floor joists & pull the pipe through, don't make the holes too tight, plastic will flex alot more than copper when it heats & cools down, personally i use a 28mm hole for 22mm & a 20mm hole for 15mm

 

[Terrywookfit]

Also hire a drill with a 90 degree chuck to get the holes horizontal.

 

[Whitespirit66]

Yes, auto by pass sounds about right. Basically, what happens if all the radiators where turned off and the boiler was on?

It's a combi boiler and I have a mix of valves, most are thermostatic.

Also, what's your take on flexible pipe? It's going to be a nightmare pulling up the floor sheets so I can run the flexible pipe through the joists while I have the ceiling down.

Your boiler may well have it's own bypass. If you have a room stat, there shouldn't be TRVs on the rad(s) in that room - so always an open route for flow.

If you have ceilings down, plastic barrier pipe will be OK through holes in joists. As said, allow reasonable sized hole for pipe and make sure holes are opposite each other - not off centre. Will make feeding through easier.