New lowest point in CH

[Steve]

As part or the refurbishment here, I am installing a couple of vertical radiators either side of patio doors.

The pipes have to go over the top of the sleeper walls (which is the present arrangement) , but then will have to dive under the joists to go across the room to the new radiators i.e. perpendicular to the joists. This will create a new low point. I know that I should put a drain valve here but I can't because it would then have to go outside at ground level.

I won't be taking pipes through notches or holes in the joists, because it would weaken them (see my previous thread "Joist Strength"). I intend to use the fat insulation foam sleeves that are recommended for underfloor pipes and it would be impossible to accommodate them on, or within, 4"x 2" joists.

I would like to use 22mm pipe to as near the radiators as possible with a short tail of 15mm up to the radiators. Pipes could be at slight angle upwards to radiators if necessary to encourage air to collect in radiators rather than pipe but I don't think that this will be the problem.

I realise that this will create a sump and presumably over time, gunge and crap will collect in these pipes.

Is it likely that this would create a problem that an occasional flushing, if necessary, could not solve? Corrosion of the pipe is my main worry.

System will be treated with Fernox.

Thanks for any input.

Steve

[John]

Surely a good opportunity to fit a drain point - to the outside.

[John Stumbles]

The pipe itself shouldn't corrode.

22mm pipe will have water running slower so be more likely to allow passing crud to deposit. 15mm should be OK for the largest rads.

[David Hansen]

On Mon, 29 Oct 2007 19:33:51 GMT someone who may be Steve wrote this:-

Why does that prevent you from fitting one? Below ground level would be a different matter.

Why do you want to do this?

[Steve]

I am concerned about freezing and insulation of the drain point outside.

Otherwise, I would have no problem with doing it. In fact there would be advantages to having a drain point outside.

How is it normally done... presumably a box for protection and to keep the insulation dry? Any pointers to something suitable.

I have read on this group, in the past, people suggesting using 22mm as much as possible.

Also, I have the pipe, fittings and insulating sleeves now :-(

Steve

[RobertL]

I can understand that.

But you could have no insulation just for the portion of the pipe that goes through the joist. you don't have to cut a 4" hole in the joist to fit the insulation as well as the pipe.

[David Hansen]

On Tue, 30 Oct 2007 08:45:52 GMT someone who may be Steve wrote this:-

This depends how you do it. If the drain valve is inside then there will be no water in the pipe which goes outside. There is thus no water to freeze and expand.

If the valve is just outside then an ice plug may form from the valve to a distance inside. If there is enough pipe for this ice plug to expand into then it is likely no damage will occur.

Greatest economy, in terms of initial cost and subsequent heat losses, is obtained by using the smallest diameter pipe which will carry the necessary power while limiting water velocities to acceptable levels.

In "conventional" pipework 15mm is fine for one radiator and often fine for several. With microbore 10mm is fine for the largest radiators and 8mm, fine for most radiators.

[David Hansen]

On Tue, 30 Oct 2007 02:07:51 -0700 someone who may be RobertL wrote this:-

Indeed. Wood is a reasonable insulator and was used as insulation material for centuries.

[<me9]

Drain point (1/4 turn valve) inside, running to slightly downwards running pipe to outside. Then you don't need insulation outside as the pipe is dry.

[Ed Sirett]

I think you are being a bit over cautious. Put ONE drain point somewhere in the lower end of the pipework put you in the top 80% of installations. Putting TWO in and/or outside and you are in the top 20%.