New kind of P trap for under the sink

[snail powered]

Never enough cabinet space?

http://www.hepvo.com/

[Maineah]

That's pretty slick now you don't have to worry about the "P" drains drying out and stinking. It also eliminates the need of a dump vent in the plumbing.

[WME]

You still need a vent in the tank.

[WME]

Not worried about negative pressure, its positive pressure that is the problem. Like going from sea level to your fav camp ground in the mountains. If there is + pressure you sink wont drain, or the + pressure will push the water out of a regular p trap some where else. Or think of the fun draining a waste tank with pressure in it

[Maineah]

You do need a roof vent you don't need a gray tank drain valve vent because of your new trap (boy that's a mouth full) it is attached to the plumbing some where under there it's for dumping the gray tank it allows air into the plumbing so when you dump the tank it does not suck the water out of your "P" trap (if you still had one). If you don't have a roof vent the sink will not drain worth a hoot no matter where you are. Think about it, the water running into the tank displaces air in the tank put enough in it will pressurize the tank if it has no place to go and you can't just vent it inside it will stink. Your new trap is a water less trap neat trick but it's entire purpose is to keep your drains from stinking it does not vent your system. You may get away with it on a public system but it is not an acceptable method even houses have roof vents.

[WME]

I go from 1600 ft to over 9000 on a regular basis, I very fimilar with what altitude changes do to a sealed container (soda bottle, tube of hand lotion) so I can make a very good guess as what would happen to a sealed tank with 10 gallons of fluid.

Even a 1/2" vent would solve all your possible problems. Normally that small of a vent would not work with a normal p trap, because it would restrict the air into the tank when your dumping, but this new design would let air in as fast as the tank empties.

Never thought about draining into a sealed tank, but Maineah is right there too.

[WME]

If your tanks (black, gray) are close togather you can T the gray tank vent into the black vent to reduce the number of things sticking through your roof.

[WME]

UH, your black tank vent is still there, Right?? The vent should be on the top if the tank and the stack should run up a wall or in a cabinet/closet

[Maineah]

There is a NFPA standard for RV tank venting and I think you'll find they require a 1 1/2" pipe. If you dump your sink into a 1.25 to 1.75" drain pipe and only have a 1/2" vent it will drain slowly. Odor in a motor home is not fun, more then any thing else the problem is exasperated by opening a vent window while you are moving.

[WME]

With a "normal" p trap the 1.5" vent is needed. BUT with this new style Karin is talking about draining the tank won't be a problem because her P trap will vent the tank during draining. As far as emptying the sink I think the the new trap will be the slow point and not the tank vent.

As far as the stinkies we'll know, when she knows.

One of the wind vane vents on the black tank vent will take care of almost all the smell problems there.

Or these guys newer answer https://360productsnorthamerica.com/site/rv_vent_faqs

[Maineah]

Lets do a scientific experiment as it relates to diameter of a tank vent versus a drain diameter as far as air displacement. Head on over to the local 7-11 and buy a Big Gulp. Put the lid on it and insert the straw. Take a nice big drink, now note the difference in the size of diameter of the vent hole in the lid versus the diameter of the straw.

In my case I am talking about venting the grey water tank which is not a big stinker. A few deodorizing tablets in that tank will easily take care of any smells. I would not consider reducing the size of the vent on a black water tank.

As to smells coming in a window .....any window open forward of the vent won't be drawing in smells from a tank vent while under way. Any window on the opposite side of the rig won't be taking in the smells either. Common sense prevails, don't open a window aft of the black water vent while underway unless you happen to own a Sunrader with a roof shape that directs air off the back of the rig rather than spilling it over the sides and don't open the roof vents while under way unless the black tank vent is aft of the roof vents. And if you are getting smells while sitting when the roof vent is open then get some deodorant in that tank!

Yes but you are creating a vacuum with the straw now blow into the straw and the big gulp lid will pop off! Same effect as pouring water into a close or poorly vented tank. You can't dump water from a 1.5" drain and expect it to drain if you are only displacing it with a 1/2" vent. When you double the diameter of a pipe you are increasing it's flow by a factor of 4X. You have to at least match it or it will drain slowly. Stink is not the issue it is the ability to drain. In the case of your new trap it can provide air to drain the gray tank that is not a problem because you don't care about sucking your traps dry but it's draining the sink or shower into the gray tank that becomes a problem if your vent is too small the air has to go some where. Yes it will eventually drain if you don't mind all that stuff floating in your sink for awhile or it belching air up through the standing water. When you open a vent window while moving the cabin pressure drops to a lower pressure then the outside air (you have dealt with planes you know what happens with air leaks) so if there are any gasket leaks it pulls the fumes into the cabin not a good thing that's why the weather vane things work so well it lowers the pressure in the tanks to a point below the cabin pressure or a least equal to.

[Maineah]

Now if you want to talk about motorhomes having to meet the standard plumbing codes then you will find that a large percentage of toyhomes are in violation of the plumbing code

(f) Vent terminal— (1) Roof extension. Each vent pipe shall extend through its flashing and terminate vertically, undiminished in size, not less than 2 inches above the roof. Vent openings shall not be less than 3 feet away from any motor-driven air intake that opens into habitable areas.

If you have a powered fan on top of your motorhome and it has the ability to bring air into your rig and the vent stacks are near it your motorhome does not meet national plumbing codes. No way is my crank open roof vent 3 feet away from my grey water tank vent. And the crank open vent in the bathroom is even closer than that to the black water tank vent. I don't have motor driven air intakes but at some point in time I might want to put a fan in my main coach vent. Guess I had better be sure it is pushing air out rather than bringing it inside.

Your house stays put so the code is not the same as a MH. Manufactures get away with a lot of things right or wrong you can't in a home. One of the best things I bought for the RV was a Fantastic Fan that reverses and has a thermostat. I open the windows on the shaded side and draw the cooler air in and vent it out the top draws about the same amount of power on low then the little thing with a small prop. and moves 10X the air.