"geraldthehamster" wrote in message
...
To clarify, these are my two options:

http://oscarthecat.fotopic.net/p54956795.html

;-)

Regards
Richard


Sorry about cutting off at the crucial moment, but got called away.

Your proposal to connect two vents into one is difficult to make properly.
It has been tried and tested many times, in many ways, by many others in the
past. They have all fallen into the trap of having both bathrooms fill with
the damp air from the other. If you are thinking of a straight connection
between the two systems, then you'll need to allow a drip trap at the very
bottom of the chimney stack to catch the water that condenses in the pipe.

To make connection between the two systems work properly, you need to bring
the lower system up to near the top of the stack. A bit like having two
separate systems, but sharing just the last bit of stack to the outside.
That way, the two systems are creating separate chimney effects (drawing
warmed air upward) on their own terms. They just join to the last foot or
so of the vent to the outside.

One system passing the other on a straight connection, would need valve type
systems to prevent them blowing air back into the room. One way flap valves
can be created using bits of plastic and things, but they usually fail to
stop all the air from being distributed between the two areas. Which is
what you need create on venting systems like the one you want.

What you want to create is a natural chimney effect from both rooms, then
create a way to force the air up the stacks to remove any moist air more
quickly when the rooms are used to shower and things. If created properly,
the system should actually draw air through the rooms without the need for
fanned assistance. The fans are only used when the air in the rooms needs
to be extracted more quickly.

If you can get both system to connect in this way, and a simple test for
this is a smoke match used to test flue systems, then you have a properly
working ventilation system. If any smoke from the match blows back into the
other room, then the venting is going to be worse when the fans are in use.

The systems will need to be tested both without fanned assistance and with
fans running, both individually and together. If any smoke testing shows a
blow back into either room, the system has failed.

Smoke matches can be got from any good plumbers merchants or Gas Supply
showrooms.

Good luck with it.