If you don't have at the kitchen sink it won't drain or at least it will VERY slowly.

As shown in the pics above, we do not have one and both sinks drain fine. It would make me very nervous having one lower than the sink bowl. You will overflow the vent if water is restricted thru the waterless p-trap. The water will equalize with the sink level.

Ours is above the sink level in fact when the grey is full it will back up into the sink and the valve never leaks. The hepo valve just replaces a regular p trap

My '13 RL is same as Shane's.

Thanks for the link! I'll definitely check the Hepvo trap. My tank was definitely not full or empty when I noticed this issue.

GipCTravelers - I don't have this additional vent at my kitchen sink either. I just have the HepvO valve installed in the vertical position just like your previous photos. My installation looks identical except I don't have the dishwasher. I do have the vents in both my bathroom and bedroom sinks but both of those sinks have P-traps.

Chris - I don't have this type of vent for my kitchen sink. I only have the HepvO trap mounted in the vertical position.

Well....I guess I get to eat a little crow pie here (at least according to this 38GK drawing)...

ON TOP of the HepVo P-Trap, this drawing seems to indicate that an under-sink vent should have been installed.

As stated previously though, ours works well without it and it's one less maintenance item we have to worry about.

It's just that with this recent find in the drawing, I see why some of you have it (and some of you don't - why?)

Surprised??

I read somewhere that if you have the hepvo valve the other is not needed. With my good memory I can't remember where
Maybe on one of your earlier links

I read somewhere that if you have the hepvo valve the other is not needed. With my good memory I can't remember where
Maybe on one of your earlier links

How do you like that....I was going by the drawing...I was feeling bad about the posting. We must be related with both of us having "good" memories...

Read page 4...Vents are NOT required when using the HepvO...

http://hepvo.com/wp-content/uploads/2017/04/HepvO-US-Technical-Design-Guide.pdf

So why is it shown in the drawing? why do some have it and some don't? Just to confuse us I guess.

RVs typically have both, and I always assumed it was to assist draining. Unlike a house, when you pull the valve on a gray tank you are ejecting the weight of that tank out of a 2 or 3" opening. It has to be able to displace that water with air quickly or it creates a suction and pulls in on the tank. The roof vent with a cap does not move that much air, nor the Hepvo.

Well after 10 months of living with a very slow draining kitchen sink including a trip to the dealer who informed me that "everything was plumbed as engineered" I decided to take matters into my own hand. Recently I also started getting sewer odor from the sink. I purchased a new Hepvo valve from Amazon and decided I was going to break apart the plumbing and figure out what was going on since my dealer obviously didn't care to investigate deep enough. I had to remove the island drawers and spice rack to reach the Hepvo and I broke apart the pipe under the sink to allow vertical movement of the pipe connected to the Hepvo. When I pulled the valve I found that the sealing sleeve was pulled completely inside out. I installed the new Hepvo and filled my sinks half full of water and pulled the stopper and my sinks drained quickly! Obviously there had to be a problem with this Hepvo from day one as my sink never drained properly from the very first time I used my brand new Redwood.

I may have been partly responsible for the inner sleeve being inverted as my sink drained so poorly that I attempted to use a plunger to try and clear a suspected obstruction. The way these valves are designed any type of suction would very likely cause the sleeve to pull upwards into itself and invert. If you ever have to plunge a line with a Hepvo plunge down to create positive pressure but never pull the plunger back up and create a vacuum. Also never use any type of snake tool as this could damage the sleeve which closes and prevents gases and odors from coming back up the pipe.

All and all I'm a bit disappointed in myself for not diving into this problem earlier and just fixing it. I guess after you spend this much money on a new RV you expect that things should work properly and if they don't the warranty should take care of it. Compound that with the fact that living full time in your RV makes it so much more difficult to take it in for warranty service. I'm disappointed that my dealer couldn't even figure this out. Oh well sometimes its just easier to take matters into your own hands.

Congratulations on your repair!

Welcome to full-timing....