Slow draining sinks & shower

Well, total guess: With the tank valve open, the tank draws air in thru the vent easier than drawing liquid thru the traps.

Doubtless someone will set me straight :)

Baffled?
Not really. You are probably serving as a vent for the campground when the valve is open, which gives a slight positive pressure in the grey tank.
Two ways to fix. Close the valve or put a 3or4' vent for the tank.
This is the main reason that you (not you personally} sometimes get that 'outhouse aroma near the RV.
Art.

I'm going to throughout another guess, like "Tin Pusher" did. It might be that your roof vent is plugged, causing differences when the valve is open vs closed. Just something to check.

Typically only black tanks have vents through the roof. Gray tanks use AAV (air admittance valves) under sinks etc.

If the valve is stuck or ?? it's hard for air to get in to help drain and as RVPAPA said you may be pressurized which will also hold the valves closed not allowing air in.

Hope that makes sense

momentum rv wrote:
Typically only black tanks have vents through the roof. Gray tanks use AAV (air admittance valves) under sinks etc.

If the valve is stuck or ?? it's hard for air to get in to help drain and as RVPAPA said you may be pressurized which will also hold the valves closed not allowing air in.

Hope that makes sense

Grey tanks have roof vents also...even with AAVs

OP........

For a 'test'

Make a 'P' trap in your sewer hose so that it has a low spot that traps water.
Open grey dump valve
With the low spot full of water....fill sink and then try draining it.

'P' trap in sewer drain hose prevents vapors etc from CG system to come up into your grey tank.



Personally........I only open grey drain when dumping and that is will full tanks and afterblack is dumped

I learned the hard way not to camp with both valves open. First 2 nights we ever slept in a camper and the smell was horrible!!! I finally figured the sewers were using our rv as a vent and the poo poo aroma was coming up through our sink. Closed the valves and the next night was much better!!

kyle86 wrote:
I learned the hard way not to camp with both valves open. First 2 nights we ever slept in a camper and the smell was horrible!!! I finally figured the sewers were using our rv as a vent and the poo poo aroma was coming up through our sink. Closed the valves and the next night was much better!!

Excuse my ignorance, what and where are these 'valves' you're talking about?

I think Kyle86 was talking about the dump valves - black tank and grey tank. The stink was able to move from the sewer connection thru the traps and into the camper. It is best to keep them closed until you are actually ready to empty the mostly full tanks.

Thanks for all of your replies. I am going to try what has been mentioned. However, as all drains are slow my feeling right now is that the grey water stack is partially plugged.

mrgreetis wrote:
I think Kyle86 was talking about the dump valves - black tank and grey tank. The stink was able to move from the sewer connection thru the traps and into the camper. It is best to keep them closed until you are actually ready to empty the mostly full tanks.

Thanks