Ongoing ventilation problems - would this work?

[GabrielKnight]

.
Hoping to exit into a sewer pipe, I want to best 4" fan I can buy that is also whisper quiet.

Using 3 x 250W, would the smallest (4") Airforce fan here be enough to clear a 2m x 4m x 3m room if always on?
http://www.growell.co.uk/p/3860/Airforce-Systems-Acoustic-Extractor-Fans.html

Using the 4" to permanently exhaust into the pipe, would you use another to intake at the other end of 4 metres of ducting?

Would the intake fan (intaking to duct, not room) need to be lower, the same or higher power than the exhaust?

Thanks!

 

[2buds]

US or UK?
In the US if you were to vent into your sewer pipes the smell would probably just exit out the roof through a vent stack.

 

[GabrielKnight]

Its the UK. There shouldn't be too many smells / fumes where I'm drilling into.

 

[hogwild]

yeah but at least the smell would be above the height of prying nostrils.

 

[GabrielKnight]

I'm hoping so. The sewer pipe leads straight into a chimney above a drain.

 

[AccountWontWork]

US or UK?
In the US if you were to vent into your sewer pipes the smell would probably just exit out the roof through a vent stack.

That's incorrect.

The sewer pipes go down to the sewer. The vented air is pushed into the local sewer sytem, away from the location of your grow.

Simple as that...

However, you have to be carefull when venting into your sewer! If your fan is not on constantly, methane and other noxious gases can seep into your dwelling!

__________

That fan looks pretty powerfull. I don't think you would want to put another fan on the opposite end of the ducting. Adding two fans propelling air in the same direction can cause drag on the fans, and will require a larger intake on the opposite end of your grow box. I believe adding just the one fan would be the way to go.

 

[GabrielKnight]

Thanks!

And would a 4 inch fan system, always on, be enough to clear a room that size?

I'll probably be using 4 meters of ducting.

The intake goes on the floor and the exhaust as high as possible, right?

 

[Guest]

I would suggest a one way damper to prevent noxious gases from coming back inot your house in the case of a power outage

 

[screwdriver]

I think pushing air thru a 4" sewer pipe of length is difficult, but do keep the air moving in one direction if you try. That smell is worse than a grow room smell.

 

[2buds]

That's incorrect.

The sewer pipes go down to the sewer. The vented air is pushed into the local sewer sytem, away from the location of your grow.

Simple as that...

However, you have to be carefull when venting into your sewer! If your fan is not on constantly, methane and other noxious gases can seep into your dwelling!

I guess it depends on where you cut into it. I was thinking about a 4" drain in a wall, yes water would flow down but air would look for the path of lease resistance which would be up the pipe where it vents out the roof. Now if cut into a 4" drain that was in the crawl space coming off a toilet or something maybe it would stay in the pipe. I'm not a plumber by trade but just thinking about how the vent pipes and stuff are made. All plumbing has at least one vent stack somewhere. It sure would suck to fire up the fan and your toilet starts bubbling. Who's farting in the drain?

Not arguing just thinking. Either way, damn good point about the sewer gases reversing if the fan was turned off, damn good point.
Peace