Hi,

I may be attempting to fit a 2 port valve to my gravity hw this
weekend. However, placement of the valve may turn out to be a problem.

I know that the valve has to go after the venting pipe, so the options
are....

Between the venting pipe T and the cylinder - Impossible, as there is
only a few cm of space between the two.

On the return, after the cylinder, very difficult for a relatively
amature plumber like myself. Access at the bottom of the cylinder is
limited, and the return pipe comes out of the bottom of the cylinder
and bends all over the place to go through the floor and return to the
boiler.

I was wondering if an easier option would be to move the t fo the vent
so that its lower down, and then i can fit the valve above it.... for
example.. cue cruddy ascii art

Current system

_____ |vent
| |
cyl |---|
| |
| | flow

New layout

_____ |
| |vent
cyl |---| |
| | |
| V |
| |__|
| |

V is the 2 port valve
Is there any problem with the vent t being lower down the flow pipe?