What size extraction fan in enclosed toilet

atlantis3, Jan 18, 8:27pm
I'm changing the ventilation in a internal fully enclosed toilet (it has no windows) single toilet. Just a standard single size toilet. Right now it has a large duct that travels about 5 meters to the out side and it works well but I want to remove the large grill and gib the hole and replace with a fan that comes on with the light switch and will run on for a few minutes when the light goes off.
What does the building code say about air change?
Is 85 cubic metres per hour ok or do I have to get a bigger extractor?
A 100mm manrose extractor does 85 and a 125mm does about 120 --- 130.
vivac, Jan 18, 8:35pm
100mm dont really work well, 125mm minimum.
tweake, Jan 18, 8:44pm
not sure on the rules but i don't think a fan is required.
fans are mainly for wet areas rather than smelly areas.
a small fan will flow more than enough air of the ducting is decent and there is a fresh air inlet.

afaik for ventilation you only need around 0.32 air changes per hour. so 1 cubic meter per hour fan would be ok. so the 100mm fan would be massive overkill, tho you will loose some flow with a long duct.
shanreagh, Jan 18, 8:57pm
It was a requirement in a recent bathroom rebuild reno that the enclosed toilet had an extractor fan & it is connected to the light switch. Builder says he would have put one in even had it not been required.
clangie, Jan 19, 6:18am
tweake wrote:
not sure on the rules but i don't think a fan is required.
fans are mainly for wet areas rather than smelly areas.

must have ventilation in a toilet-either fan or window
ryanm2, Jan 19, 8:31am
Fans are 100% required for enclosed toilets.
budgel, Jan 19, 8:39am
Given that a toilet space .9m x 2.4m x 2.4m equals 5.184 cubic metres, I think the smaller fan would be OK as long as there is adequate room for fresh air to come in. Probably the gap under the door would be the limiting factor.
85 cubic metres an hour equals around 1.4 cubic metres a minute, so it would take around 4 minutes to change the air if everything was perfect, so give it 5minutes, which is quite a long time for the fan to be on. Your choice!
ira78, Jan 19, 10:17am
I doubt anyone anywhere has ever walked into a toilet after someone else and wished they had a less powerful fart fan.

Especially if you're putting it on a timer, go with a decent sized one.
tweake, Jan 19, 5:48pm
yeah that.
doesn't matter what size fan you have if the air inlet into the room is restricted. likewise wise with long ducting. plus keep in mind a lot of fans push air better than they pull air.
seen plenty of homes where the door seals pretty well to the hallway carpet, which means the fan doesn't do much at all.

if you want to not hear bathroom noises i suggest installing an air inlet as well, possibly tied to a ventilation system or simply a jumper from the toilet to the hallway.
a neat trick with some ventilation systems is to have the house air flow exhaust permanently through the toilet.
atlantis3, Jan 20, 5:20pm
Thanks everyone.
I contacted Manrose who make the extractors and they said the building code calls for 25 litres / second for a residential toilet so the 125mm fan is required and their extractor has the built in adjustable run on timer.
nicc4, Jan 20, 6:58pm
Any chance of the sh!t hitting the fan?
bryalea, Jan 20, 8:09pm
You are implying people shut the door when they use the toilet. Very rare occurrence here.
peanuteater, Jan 20, 8:10pm
nicc4 wrote:
Any chance of the sh!t hitting the fan?[/quote
Stand up comedian ]
ira78, Jan 21, 7:40am
How do you even get away with shutting the door? Do these people not even have cats or dogs?
gilligee, Jan 21, 10:04am
Don't know anyone or been anywhere where they don't close the door!
nzjay, Aug 23, 2:53am
A fan can only suck/expel what ever can be replaced in a sealed room. So, if the door is shut and reasonably sealed you might struggle to get 1 air change in 5 mins! Not many options, but cutting 10mm off the bottom of the door works, or fitting a louvre grill into the lower part of the door perhaps.