Sewer Outlet Pipe Release Valve??

[ATCguy]

Has anyone ever installed a pressure release valve into their sewer pipe?

Here’s the issue...

I mainly travel in the west these days... constantly changing altitudes as I make my way back & forth around the Rockies. With these changes in altitudes come vastly different temperature & air pressures from one location to another. Let’s take my latest move as an example...

Before finally leaving my winter camp in Arizona, I dumped the black & grey tanks. I even kept the drain valves open for an extended period (15-20 minutes, or so) to get them as empty as possible. No issues... and when I removed the sewer hose from the rig, nothing was draining from the outlet.

So I get on the road and begin traveling to my next destination, which happens to be at a location significantly higher in altitude than my previous one. I was around 800’ MSL on the Colorado River in Arizona... and am now at 5,100’ MSL here in Wyoming, but traveled as high 8,200’ MSL during transit.

Now, even though I allowed those tanks to fully drain earlier... I know that due to the normal jostling on the rig during travel that I might find some fluid had seeped into the outlet pipe once I arrived. And, having experienced the following before, I was prepared for it.

When I went to connect the sewer hose to the rig... and I begin removing the cap... BOOM! The pressure inside the pipe literally blew the cap off as soon as the cam locks were released... spewing all of those residual liquids out at high speed from the outlet.

Like I said... it’s happened before, so I knew to be well out of the way.

I understand why it happens, as with the black & grey tank valves closed during transit, there’s no venting available for the pipe... but I figure there’s gotta be a way to keep that from happening.

I’ve thought of leaving the 2nd grey tank valve open during transit... but again, with the jostling of the rig rolling down the road, I figure even more grey water that maybe didn’t fully drain while sitting static could end up in the pipe upon arrival.

Which then leads me to the question posed: has anyone ever installed, or heard of anyone installing, a pressure release valve into the 3” sewer outlet pipe?

I did a cursory search on Goggle, and on another RV forum... and the only release valves discussed were for the water heater, and other assorted fresh water systems.

So just curious... any ideas?

[Revere411]

I added one of these.
https://www.amazon.com/dp/B000BGHYJS...p_mob_ap_share

[Revere411]

Originally Posted by Revere411

I added one of these.
https://www.amazon.com/dp/B000BGHYJS...p_mob_ap_share

Then I can close this and if I ever needed to I can open both grey tanks and voila I have one big tank. Then when I go to dump I close them and open my black tank first. Then open them back up to rinse everything out. With this valve there are no more residual suprises.

[franktafl]

I put a twist on valve on mine since the valve for the black tank was leaking and there was a bypass. I have a question, do you have a plumbing vent?

The plumbing vent, also known as a vent stack, helps regulate the air pressure in your plumbing system. Just as drain pipes remove water and waste from your home, the plumbing vent pipe – also known as a plumbing air vent – removes gas and odors.

[Revere411]

Originally Posted by franktafl

I put a twist on valve on mine since the valve for the black tank was leaking and there was a bypass. I have a question, do you have a plumbing vent?

The plumbing vent, also known as a vent stack, helps regulate the air pressure in your plumbing system. Just as drain pipes remove water and waste from your home, the plumbing vent pipe – also known as a plumbing air vent – removes gas and odors.

All the tanks have vents. I believe that what he is referring to is pressure building up between the tank valve and the termination cap. The 3" pipe between the two does not seem like it would make a difference but the water bottle that I open at sea level then drive to 8000feet says different. Lol

[pctomlin]

After changing altitude you could open the grey tank valve to equalize pressure. I added a permanent valve on the grey/black outlet line, learned my lesson when my black tank valve leaked, yuk. It is handy to backwash your full grey tank into an empty black tank to break some more crap loose literally when dumping.