looping of pipes

[Jupiter01]

I wonder if someone can advise me on a arrangement of 15mm flow and return pipes that I need to route.

I am planning to go vertically down for approximately 25cm and then a 90 degree bend to turn horizontal for around 35cm and then another 90 degree bend to take me vertically up for around 50cm. It's a "u" arrangement of pipes.

Some guys have told me its not an issue at all whereas others have said that it will cause air locks.

I would appreciate your views on this.

 

[45yearsagasman]

A downward facing "U" arrangement would not normally pose a problem, if installed as you describe. There are many times that I've done that to avoid an obstruction when running rad pipework.

 

[FiremanT]

A downward facing "U" arrangement would not normally pose a problem, if installed as you describe. There are many times that I've done that to avoid an obstruction when running rad pipework.

provided that the horizontal pipework on both sides of the "u" can ultimately vent.

 

[fatplumber]

To help you, air will rise to the closest high point unless the pressure is enough to over come its inertia. So a pipe that goes up then down will have a bubble of air at the top of arc. The air will not be able to escape and water will not pass by. If it goes down then up, then the air will escape and not block the pipework. This is not a problem on mains water, shower pumps or micro bore heating.

 

[Jupiter01]

You guys are absolutely brilliant. Very helpful. Many thanks first of all!
I thought a picture may help. The thick red line denotes the 22mm copper flow and return. You should then be able to see the RSJ at the end of this run. There is a void on the other side of this as I have a lean to roof. I want to get into that void with my 15mm pipework as I can then drop down to the two rads under the windows (below the void described above).
The thinner drawn line shows the route I am taking (The "U" I referred to). As you can see, I am planning to come down slightly, across the bottom of the RSJ and then back up into the void and across to feed the two rads on that wall. I have out a rad drop in the picture to illustrate this too.

All of this pipe work will either be in the wall, behind drywall or under the ceiling boards and hence inaccessible.

Are you still happy with this?

Thanks again.

 

[fatplumber]

I refer to my post, you wil have air trapped where it rises then falls. With experiment, you will learn how to blow it out but I think you would do better to keep the pipework below the joist.

 

[Jupiter01]

Thanks. I cant be below the joists as I want to coneal the pipes. I've managed this everywhere else. I understood your explanation on air locks but my slight confusion is that, I don't have a rise and fall. Wouldn't that be an 'n' as opposed to the 'u' that I've indicated in the picture?

 

[Nige F]

If there is going to be a rad in the room above in the same place i.e your drops on the wall go --I it'll be ok and vent upstairs. excuse the effort at creating a diagram

 

[gigz]

If its gonna be on a pressurised system it'll be ok once the systems vented. If its on a gravity system it might cause air issues but i doubt it.

 

[roguetrader]

Why not put the pipework down on the floor before its screeded?

 

[Jupiter01]

There will be a rad above but that's on a different zone and hence different pipes. So there will be no vents above. It will be an unvented cylinder based system
Unfortunately, the floor is already screeded.

Am I okay do you think?

 

[denso13]

Reduce to 15mm before the RSJ and drill holes in the beam to take them straight through. Two holes for 15mm pipe won't impact on a beam that size.

 

[Jupiter01]

Really? Drilling through a structural beam didn't even cross my mind. I've got upstairs resting on this. You may sense that I'm a touch nervous about doing this

 

[fatplumber]

You'd be amazed at how much metal you can remove before the steel is weakened.