I'm having some issues with my current bathroom extractor set up. I have a bathroom with shower and toilet and a separate toilet next to it. At the moment they each have one of those small inline 100mm(80m3/hr?) extractors in the loft feeding into a Y piece the into a 110mm vertical pipe through the roof. All this connected with tumble dryer hose. This set up came with the house.

The genius who fitted this lot didnt give a lot of thought to the condensation that would be caused in the uninsulated vertical pipe and to be fair neither did I until today when one of the looped tumble dryer ducts came away from the weight of water collected in it.

So....... having done a bit of research i think the extractors are very under sized and I definitely need to fit a condensation trap to the bottom of the vertical pipe.

The question is i like the idea of fitting one large extractor for both the bathroom and toilet, using say a 6" extractor. This would be fed by 2 100mm feeds from the two rooms and then to the 110mm vertical roof pipe. Obviously the flow rate of the fan will be reduced because I'll need a reducer to fit the fan to the 110mm, but I'm assuming it should be higher than the biggest 100mm fans?

Is this a reasonable way of doing it or am I better sticking with 2 fans into the one vent pipe and upgrading them?

Bathroom is 15m3 and toilet is 3m3.

Sorry for the long post. But hoping the locost collective might help.

Thanks.

how do you intend to switch the single fan?
or is there a position local to both doors to locate the switch? if you 2 way the fan from 2 positions and it has an over run. you'll never know if its on or off!

If possible I would run two separate duct runs. Use one through the roof and the other through the outside wall or to the eves. The joining of two together is not a good idea. You can buy a whole house vent kit but it may be a bit extreme for two rooms.

If going with a single fan it would be switch via a couple of relays.

Unfortunately putting an extra duct run is probably out as I havent got eves and i dont fancy hanging off a ladder boring 100mm holes in my brickwork. Not because I'm lazy just not as good at hanging off ladders as i used to be.

Thanks for the answers.

I'd just put one fan in the bathroom. The toilet is not going to have a substantial amount of vapour produced to need forced ventilation.

Direct through the wall is best, as there is less resistance and less chance of condensation in the pipe. If you have to leave it going through the loft, just insulate the pipe to keep it warm.

Forgot to point out both rooms have no windows.

Dont forget that you need to allow air infiltration into the room, so make sure that you have a gap under the doors, or an brick etc.

A friend of mine used to be into farm machinery. So, now he's an 'ex-tractor fan'!!!

Surely the answer is simple. Don't use uninsulated ducting. Get ye on Ebay and get a load of insulated hose. Very cheap from certain purveyors of hydroponic equipment- amazing how many people grow tomatoes indoors.....

If you vent it all outside and it's well insulated the only condensation that's going to occur will be outside the building.

Re the Y piece- best to have it just before the outlet through the bricks.

And wear gloves when you handle the insulated hose. Got a bit blase using rockwool insulation- the insulated hose is usually glassfibre and gives you a good old rash if you don't. Guess how I know....

As mentioned, use insulated ducting. also use non return valves in the Y piece so that you aren't just blowing from one room to the other.

The best fans I have come across are made by Envirovent

Mookaloid- Yep those were the fans I was looking at.

I get that the insulated ducting will help with condensation but the main problem I think i have it that the existing fans have so little puff to them that they're struggling to extract and then push the air through the ducting to the outside world.

Non return valves and condensation trap will be added.

Thanks