Opinion on venting grey tank.

[Oscar1]

a tank is going to stink. the higher up we launch that smell, the less often we come in contact with it.
__________________
Um I think that's what I said.
Glad your 1/2" pex line vent is working for your needs.
You take care now.

 

[Rovobay]

Cool ideas. I think I will vent out with the black tank and will run the vent under the bus to the black vent location.

 

[Rovobay]

for future reference. I think this will be the route I go. Thanks for the idea

 

[JDOnTheGo]

for future reference. I think this will be the route I go. Thanks for the idea

That appears to be a very complex alternative to an air admittance valve - which are very easy and inexpensive.

When you open the 3" valve to dump your tanks, a good sized vent is going to make a huge difference in how well your tank dumps (a rapid 'whoosh' helps wash out the the solids).

At a minimum, an elevated (roof) vent should exist. Another (small) vent located elsewhere can be a very good thing to get air movement. I've used the "Cyclone" vent cap for years to get a tiny bit of vacuum (on the roof) to aid air movement.

You will hear RV people frequently talking about how much their tanks/toilet/bathroom stinks. I suspect that is generally due to inadequate/improper venting and/or poor maintenance (broken air admittance valves).

 

[Rovobay]

That appears to be a very complex alternative to an air admittance valve - which are very easy and inexpensive.

So you are saying all I would need is something like this?

like this product from amazon?

Does there need to be any further venting from the gray tank or just this product? Thanks...

 

[JDOnTheGo]

So you are saying all I would need is something like this?

To provide a vent to each sink, yes. You can get away without them but could have issues the water not draining properly.

Does there need to be any further venting from the gray tank or just this product?

Yes, you need at least one large diameter tank vent (preferably to the roof - but I know exceptions exist). I suspect it varies but I believe most RV's have a 1.5" vent (for each waste tank).

 

[Oscar1]

So you are saying all I would need is something like this?

like this product from amazon?

Does there need to be any further venting from the gray tank or just this product? Thanks...

Thes are not vents, they are one way diaphragm valves to allow air in only so that the sink can drain properly. You still will require a vent from the tank.

 

[Danjo-SKO]

for future reference. I think this will be the route I go. Thanks for the idea

That’s cool. I like it, though complex

 

[JackE]

for future reference. I think this will be the route I go. Thanks for the idea

Ok, I'm no Mario, but I have done plenty of plumbing in my houses through out the years. Someone please explain what the heck I'm looking at? Why not just bring that vent in the wall straight down into the drain line? What does all that extra crap there do? Aside from having a clean-out access in the line which could just be done in the main line from the sink.

 

[FatBoySTL]

Ok, I'm no Mario, but I have done plenty of plumbing in my houses through out the years. Someone please explain what the heck I'm looking at? Why not just bring that vent in the wall straight down into the drain line? What does all that extra crap there do? Aside from having a clean-out access in the line which could just be done in the main line from the sink.

This is meant for kitchen islands that are not backed by a wall. It gives you an option to plumb a true vent (instead of an air admittance valve) when there is no direct path to the roof available. The twin lines and high loop allow air in the top while water drains out the bottom.

 

[turf]

a waterless p trap like a hepvo is a self venting fixture. no air admitance valve needed. an rv toilet is self venting, no air admitance needed.

if you use rv designed fixtures, it will simplify your design. the tank still needs venting.

i do not see a reason to vent a stack of self venting fixtures.

a standard p trap in a rv is a point of failure. there are better, easier solutions.

 

[kazetsukai]

So you are saying all I would need is something like this?

This seems nonsensical. P-Trap exists to stop odors down the pipe from getting into the room, this is defeating the trap. Why not just have no-ptrap in that case and go directly from sink down to the tanks? Tt still "vents" that way.



I used these air admittance fixtures directly on my grey tanks for a while but knew they were insufficient.



Turf why do you consider a p-trap a point of failure?




One thing I need to do is install check valves on my drainage so that

• In transit there's no opportunity for (liquids with momentum) to rush back up the pipes.
• Prevent RV drainage hookups from allowing sewage backflow to rush back into the tanks/drains/cabin

 

[FatBoySTL]

This seems nonsensical. P-Trap exists to stop odors down the pipe from getting into the room, this is defeating the trap. Why not just have no-ptrap in that case and go directly from sink down to the tanks? Tt still "vents" that way.

I used these air admittance fixtures directly on my grey tanks for a while but knew they were insufficient.

Turf why do you consider a p-trap a point of failure?

One thing I need to do is install check valves on my drainage so that

• In transit there's no opportunity for (liquids with momentum) to rush back up the pipes.
• Prevent RV drainage hookups from allowing sewage backflow to rush back into the tanks/drains/cabin

The air admittance valve doesn't defeat the p-trap. It only allows air into the pipe (so you don't form a siphon). It doesn't allow the air back up.

If you're not using a Hepvo valve, you still need the p-trap to avoid gases from the tank from coming back up in the cabin. The Hepvo would serve the purpose of the p-trap, air admittance valve, and check-valve to keep slosh from coming back up the pipe.

I'm not sure why you'd use an air admittance valve directly on a tank. That needs to have bidirectional venting.

I imagine Turf thinks the a p-trap is just one more thing to rattle loose or get knocked around by shifting cargo. Like I said, the Hepvo would swap three components for 1. Simpler is always better. Of course, The Hepvo has moving/flexing parts inside, so I don't know if they're really all that much simpler long-term. I've been in a few older RVs that have worn out hepvo valves... Not particularly pleasant. What is the long term durability/reliability of the newer valves?

 

[Oscar1]

The air admittance valve doesn't defeat the p-trap. It only allows air into the pipe (so you don't form a siphon). It doesn't allow the air back up.

If you're not using a Hepvo valve, you still need the p-trap to avoid gases from the tank from coming back up in the cabin. The Hepvo would serve the purpose of the p-trap, air admittance valve, and check-valve to keep slosh from coming back up the pipe.

I'm not sure why you'd use an air admittance valve directly on a tank. That needs to have bidirectional venting.

I imagine Turf thinks the a p-trap is just one more thing to rattle loose or get knocked around by shifting cargo. Like I said, the Hepvo would swap three components for 1. Simpler is always better. Of course, The Hepvo has moving/flexing parts inside, so I don't know if they're really all that much simpler long-term. I've been in a few older RVs that have worn out hepvo valves... Not particularly pleasant. What is the long term durability/reliability of the newer valves?

FatBoy gets it!
have to agree I don't see any value on putting an air admittance valve directly on the tank. Also question the longevity of the Hepvo but that's the route I'm taking.

 

[turf]

p traps freeze in an rv. if its not winterized, it will freeze, and crack. then next year when your use you sink, the trap will leak underneath.

yes, you can fill each drain each winter with the pink stuff.

if you use a waterless trap, its not going to freeze, no pink stuff needed.

i installed 2 hepvos in my rig in 2011. one is indoor under the sink, one is outside, horizontal along the bottom of the bus, under my shower. both have worked flawlessly since install. the one outside has surprised me in its durability.

 

[kazetsukai]

FatBoy gets it!
have to agree I don't see any value on putting an air admittance valve directly on the tank. Also question the longevity of the Hepvo but that's the route I'm taking.

I have what is seen in that picture and I don't see anything to prevent air from moving bidirectionally with those. Maybe it isn't the vent (top) but a valve (just beneath it) that I'm missing.


In case it wasn't clear, my line of questioning was exactly that- questioning, not critique. Not a master plumber or anything.



Freezing traps is a good catch, I don't consider freezing in the cabin acceptable for any reason so I wouldn't have thought of it.

 

[Jolly Roger bus 223]

use air admittance valves,island vents,studor vent type stuff.
i know them so not my choice?
i have hard piped lines to the the bus exterior and install the vent above roof when camping and pull and cap when on the road.
if needed when on the road then look at well casing vent caps.
they come in many sizes and have a screen in them to prevent bugs but ideally when camping you want your vent above head level and wind definitly is a consideration

 

[Oscar1]

I have what is seen in that picture and I don't see anything to prevent air from moving bidirectionally with those. Maybe it isn't the vent (top) but a valve (just beneath it) that I'm missing.


In case it wasn't clear, my line of questioning was exactly that- questioning, not critique. Not a master plumber or anything.



Freezing traps is a good catch, I don't consider freezing in the cabin acceptable for any reason so I wouldn't have thought of it.

No one said you were being critical!
This device is often incorrectly refered to as a vent, it is not a vent.
It allows air one way only with a very light spring and rubber seal that can be overcome by the vacuum created when you drain the sink allowing for a faster drain.
Cheers

 

[turf]

Because this is a thread about venting. i will share that first.

my 1/2" pex vent and fixture.

and here is one of my hepvo valves. i stated earlier that it was horizontal and that is incorrect. my shower drain is above the fuel tank, it comes out horizontal to the edge of the tank and there i have the hepvo vertical. the drain wraps around and enters the 3" toilet stack and drops into the tank.

it is right in front of my passenger rear tires. about 9 years and 40k miles like this.

 

[Rovobay]

Because this is a thread about venting. i will share that first.

my 1/2" pex vent and fixture.

and here is one of my hepvo valves. i stated earlier that it was horizontal and that is incorrect. my shower drain is above the fuel tank, it comes out horizontal to the edge of the tank and there i have the hepvo vertical. the drain wraps around and enters the 3" toilet stack and drops into the tank.

it is right in front of my passenger rear tires. about 9 years and 40k miles like this.

Thanks for the input. any issues with odor or draining tanks?