Half cross-over - which way up?

[8aviashusband]

I want to use a half (or part) crossover in a horozontal pipe run to cross over a pipe which runs parallel to the rafters in a loft (i.e. it slopes). One side of the crossover feeds directly into an elbow connected to a pipe parallel with the one crossed over. (The reason for this is to get the flow & returns right, and this seems the neatest place to do it.)
Question is: which way up do I put the crossover? Hump up, or hump down? Either way would appear to produce an air lock - either in the fitting, or the adjacent pipework.
Any recommendations?

 

[doitall]

You should always come off the bottom of high level pipework that is going to below, or top if going to above.

So down in you case.

 

[SimonH2]

In this case, as I read it, he's not going up or down, just crossing another pipe before running parallel to it. Whichever way he puts it, the pipes end up the same way - in the same horizontal plane.

I don't think the inch of hump or dip will create any meaningful air lock - the water flow sill just carry it away. That is unless venting is reliant on a continuous slope to allow bubbles to escape from static water.

The only other consideration I can think of would be to think about whether it will affect the ability of the pipe to drain down - using a hump rather than dip may result in a 'dam' which prevents the pipe draining properly. A dip will stay wet, but the pipe could still drain if both ends are open.

 

[8aviashusband]

Thanks, SimonH2
Here's a (rough) picture of what I have in mind. This was just lashed up dry, the short bit of pipe will be longer, and the joints soldered!
View media item 53176You can see, there will be a small air lock either in the elbow if I do it as in the picture, or the crossover if it's the other way up.
As you say, its probably not enough to worry about.

 

[doitall]

Thats fine and the correct way to do it. Although it would have been better to cross them over where you turn to drop down so the crossover was in the vertical.

 

[CBF]

that's posh for a roof space, don't you know how to hand bend

 

[hansthebear]

If you are going to insulate these pipes i would space them out a bit more