odor while driving, negative air pressure, venting... SOLUTION???

[Don4107]

Your toilet may have an overflow prevention drain hidden under the rim.  Try filling the bowl completely to see if has one.  If you can't overflow the bowl it has a drain. It may have a built in trap that needs to fill with water to block odor. 

Even if it has a trap, it may suck odor past it with enough negative pressure. Some just silicone the hole closed. Just be aware that a leaking inlet valve can cause a overflow if you plug the drain.

Good luck

[sledhead]

If I can keep a little water in the bowl no smell ya good luck . tried new seals lots of grease heck my wife even tried to shrink wrap it. The smell still comes up if the windows are open .

I like the elect valve idea

keep us posted 

thanks    dave

[Larryd]

I had the same problem when I got my 4905. Rather than put a whole lot of dollars into venturi, I took the cap off the vent and put a plastic pipe  T about six or eight inches off the roof and parallel. In fact had two vents close, put two tees upthere and have no more odor coming from the bathroom.
Larry

[gus]

One thing I forgot - sometimes when the black tank is very full and then emptied it sucks all the water out of all the traps.

Probably because the vent is smaller than the drain.

When this happens we have to fill all the traps with water again.

[Frank @ TX]

We had that problem a few years ago.  Lately I installed a household toilet.  A one piece type because I didn't want the tank vibrating loose.  I adjusted the tank level so we get about a 3/4 gallon on the half flush button and less that a gallon with the full flush.
We carry 150 gallons of fresh water and 165 gallons of waste water.
When we're at a campground we seem to dump every other day or every third day.  The washer dryer use up water.
When we're dry camping we go about a week or 10 days.
This was our solution , now you can flush any time you want.
Frank

[wg4t50]

The craziest thing I found was not the lack tank but the gray tank, I keep my coach in mt garage / shop, ad pend about 3-4 hours a day in it, TV business work with internet quoting and keeping business going.  Point is, never use the head, just the sinks, in about a month take an exercise run around 20 miles, if I do not keep the gray tank treated well, the odor is horrible. While the black tank is clean and empty. A surprise that the gray tank was the issue.
Dave M

[Scott & Heather]

We had that problem a few years ago.  Lately I installed a household toilet.  A one piece type because I didn't want the tank vibrating loose.  I adjusted the tank level so we get about a 3/4 gallon on the half flush button and less that a gallon with the full flush.
We carry 150 gallons of fresh water and 165 gallons of waste water.
When we're at a campground we seem to dump every other day or every third day.  The washer dryer use up water.
When we're dry camping we go about a week or 10 days.
This was our solution , now you can flush any time you want.
Frank

Since we're on the subject of poo control, I have been considering putting a house toilet in our next coach. We love our current Dometic porcelain, but I wouldn't mind a house toilet if we could get the flush to use little water. Can you post some photos of yours please? I don't think anyone will object...after all, a throne by any other name, is still a throne 

[Frank @ TX]

Hi Scott,
I've never been able to post photos to the board.
We have a "Glacier Bay " one piece , this is a Home Depot brand.
Our tank is right below , so the water is used to clear the bowl not to carry the waste thru the piping.  Because of this I was able to adjust the water use quite low in both the half flush and the full flush.  Hope this helps.
I you still want a photo I can email you one.
Post your email address and I'll sent you a photo.
Frank