Grey Tank to Campground Sewer?

Ascape Artists

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Nov 18, 2025
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Beverly
My camper only has a gray tank. Is it okay to connect the gray tank to the campsite sewer connection or will I get a gas back up? Clueless and will accept all advice please.
Thanks,
ML
 
Every sink and the tub/shower will have a "P-trap" or similar feature to block sewer gases coming in so you are perfectly ok to leave the grey connected and open. Unlike the black tank, it's ok to keep grey open so water flows out as soon as it goes down the drain. Or you can leave it closed and just drain when necessary - either option is ok.
 
If you do leave the gray valve open, make a U shape in the sewer hose to hold some water like the P traps do for your drains. That not only blocks odors but most sewer systems also contain sewer flies that sometimes move up into your waste tanks to breed.
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Every sink and the tub/shower will have a "P-trap" or similar feature to block sewer gases coming in so you are perfectly ok to leave the grey connected and open. Unlike the black tank, it's ok to keep grey open so water flows out as soon as it goes down the drain. Or you can leave it closed and just drain when necessary - either option is ok.
While that is true have you ever seen the adds for do nothing black tank chemicals that show the stinky RV.

Guaranteed his gray valve is open the stink goes into the tank and up the vent.
 
Joezeppy is right but Kirk's suggestion is a smart one. Best to keep the odors (and maybe sewer flies) as far away as practical. Sewer flies can lay eggs in the tank and remain a nuisance long after you have unhooked the hose and moved on. It doesn't take much to make a "hump" in the sewer hose to form a water trap. No special gear needed, just a piece of firewood, a stone, or whatever is handy.
 
I'm assuming that you have a handle to open and close the tank to empty it. So leave it connected but only open it when the tank is close to full. Then close it again.

I'm assuming its very rare not to have a black tank?
He has a Aliner. either no toilet or maybe a composting toilet.
The only other problem with leaving the valve open is a build up of soap scum and food particles. It needs the force of water to help flush the gunk out.
 
I'm assuming that you have a handle to open and close the tank to empty it. So leave it connected but only open it when the tank is close to full. Then close it again.

I'm assuming its very rare not to have a black tank?
Our Lance 1575 has been converted to a composting toilet. No more messing with a black tank. We hook up to sewer but leave the valve closed until about 3/4 full, then empty. No vent smells or sewer flys.
 
If you do leave the gray valve open, make a U shape in the sewer hose to hold some water like the P traps do for your drains. That not only blocks odors but most sewer systems also contain sewer flies that sometimes move up into your waste tanks to breed.
View attachment 2446984
by sewer gasses it can stink the whole park is you leave its open and make that sag in the hose
 
gases goes right the hose to your tank then through the roof vent. That vent is to allow your tanks to drain fast. We,ve all walked through a rv park and you smell the sewer gas, Thats because someone has left a valve open without creating P trap with the sewer hose. My first answer was not complete-it should have said- if you don't make your sewer hose sag.
 
gases goes right the hose to your tank then through the roof vent. That vent is to allow your tanks to drain fast. We,ve all walked through a rv park and you smell the sewer gas, Thats because someone has left a valve open without creating P trap with the sewer hose. My first answer was not complete-it should have said- if you don't make your sewer hose sag.

OK, Corrected, but Kirk stated a trap in the hose.
What you are saying is no worse than someone not using screw in adapter or 'doughnut' on sewer fitting. I've seen a lot where they just shove the hose or elbow in the "hole".
Those are probably the odors you are smelling.
If the campground follows code, there should be a trap in the ground at each inlet to prevent gases from escaping.
 
If the campground follows code, there should be a trap in the ground at each inlet to prevent gases from escaping.
I think the trap requirement applies only to residential or commercial buildings outlets and not to exterior branch line connections. The campground connection port is essentially a clean-out (which also does not need a trap). However, it is supposed to be a sealed connector, either with a plug when not in use or a leak-free connection when in use. Many jurisdictions require a "rubber donut" if the connection is not via a threaded adapter.

Popular perception aside, properly operating septics typically have little or no odor anyway.
 
Thank everyone of you for weighing in on this post. Maiden voyage in 2 weeks, finally time to put these suggestions to use. Kennebunkport beware! Lol
Is that in Maine? If it is, don’t forget to drive by and see the President Bush’s compound. Are you staying at the Red Apple Campground?
 
Popular perception aside, properly operating septics typically have little or no odor anyway.
While that is true, many RV park sewer systems do not connect to a septic system but to the city sewer system where there is ample supply of sewer gas.Sewer gas is a mixture of gases produced when organic waste breaks down in low‑oxygen (anaerobic) environments such as municipal sewer lines, septic tanks, and home drain pipes.
 

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