Hi
My Separett is still waiting to be fitted
But, I had been thinking that since there is negative pressure behind a vehicle when driving that the vent from the toilet, if vented through the back wall, might produce its own suction?
If you mean directly between cab and camper that might also mean negative pressure, and/or possible engine smells entering the camper?
I suppose which fan wins depends on how air tight the camper is as a whole. If the only way for air to enter or exit are the two vents you mention in your bathroom then it will just be which ever fan is more effective. The 24v fan I was given from Separett is just a small pc fan.
If you had a window open at the time then they would probably both extract normally?
As mentioned elsewhere, the main reason for the fan within the toilet seems to be to dry out the contents. I don't suppose it matters much which way the wind is blowing for that at least to take place?
You can run the toilet vent anywhere you like, but from memory two 90 degree bends only are allowed for it still to move enough air, and it's about a 3" pipe. If you ran that straight up and out of the toilet roof you could use the same fan for both, with a Y splitting the pipes so sucking from both the toilet base and from the ceiling area in the shower? Or a weaker constant fan complementing a stronger one during showering, but pushing the same way out of the same hole?