Unused legs in a central heating system?

[Mathew Newton]

Apologies for the rather cryptic title...

I am in the middle of creating an open-plan kitchen/lounge/dining area and cannot with certainty decide where best to put the radiators. Indeed, I can envisage that the 'best' position might well change over time if/when the more mobile elements of the room move around.

I was wondering, therefore, if there would be any issue with me piping up a couple of areas to cater for the potential alternative siting of radiators at a later date? In keeping with the rest of the system I'll be using 10mm plastic piping run down from the ceiling behind the plasterboard so it'll be a straightforward job to do at this stage of the construction (the ceiling is currently down). The exit points are are at socket height (behind where the radiator would be) so I would just cap off the pipes in a back box and cover them with a blanking plate.

Once my project is complete there will be limited access to the ceiling space so I was planning on connecting all the radiator feeds up to the manifolds now hence the unused ones will likely be sitting there for a long time with either air or water in them. Does anyone anticipate any potential issue(s) with this?

[Tricky Dicky]

From my experience with microbore systems dropped from above is their tendency to develop airlocks particularly after a drain down. Most can be solved by having sufficient drain off points one on every radiator. If you plan to leave pipes accessible behind blanking plates then providing drain offs should allow you to ensure all air is removed, once fully filled any air getting into the system should tend to collect in the tops of radiators.

Richard

[Mathew Newton]

Thanks Richard, that's good to hear (the drain off mitigation, not the risk!). All the existing radiators do happen to be fitted with drain off valves so perhaps the risk was recognised at the original design/installation stage also.

[harry]

This is where underfloor heating comes in. No radiators.

[Mathew Newton]

Indeed, but it's a bit late for that now! ;-)

Whilst part of the new space was a new extension (and hence easily UFHable) the remainder wasn't and there were various reasons I wasn't keen on retrofitting it.

[tabbypurr]

It can be an issue if you get an infection in the system, or other situation where it's necessary to empty the water in the legs. Put a drain down valve on the end and all is good.

NT

[Roger Mills]

The unused legs would be better filled with water rather than air. How about connecting each flow and return together through an isolator valve behind the blanking plate? You could then allow them to fill with water and then turn off the valves.

[Brian Gaff]

Yes when I saw the subject line I did wonder who would put wooden legs in an expansion tank!

I did consider it might be in preparation for Talk like a Pirate day on Thursday... Brian

[Mathew Newton]

I could always bleed the pipes by briefly removing the stop ends. That's one of the beauties of push-fit for me; the ease with which joins can be made/unmade. I've done many a 'live' capping using push-fit stop ends and when the pressure's on (pun intended) you can't beat a toolless fitting.

[Mathew Newton]

Hmm... infection doesn't sound good. Is that something inhibitor is design to prevent? (Of course this needs water in the legs, not air)

The pushfit stopends should serve well for that, and being 10mm fittings they are tiny so will easily fit within the standard backbox.

[tabbypurr]

it doesn't prevent it

?

sounds good

NT

[Mathew Newton]

I meant if the inhibitor is to have any effect then the pipes will need to have it in them, not air.

[polygonum_on_google]

There are people who cannot tolerate underfloor heating. It isn't the answer to everything.

[tabbypurr]

afaik there is no purpose in having inhibitor in plastic pipes - they don't rust!

NT

[Mathew Newton]

It's to protect the radiators rather than the pipework.

[tabbypurr]

and any other parts that might rust, eg boiler & sometimes other parts. Doesn't do a thing for plastic.