New Dometic 320 Stinks when Flushing

[rodgebone]

Replaced my Thetford with a Dometic 320 last month. The Dometic produces a strong odor every time its flushed. no leaks anywhere and I don't think it's coming from the black tank itself. All seals were lubed during installation. The horrible Thetford never did this. Any ideas? Thanks in advance!

[jsb5717]

I assume you're getting a strong sewer odor? If that's the case then it's not the toilet (unless it's not installed well so that gases can escape when it's sitting idle). You've likely got some build-up in the tank. When I get that I pour 10-15ish gallons of water down the toilet along with a couple Camco TST black tank packets and take the trailer for a drive to let it all slosh around a bit. Then dump it out and move on.

It doesn't happen very often because we always flush plenty of water with every use and keep a TST packet in there while in use. But if we do get the unpleasant smell then it's time for a tank cleaning.

[firestation12]

Did the box the 320 toilet came in, look previously opened? Sometimes a defective unit gets cleverly cleaned, repackaged and returned then is resold. Another way smells can enter the bathroom, is when the flush valve is depressed. If a ceiling exhaust fan is running overhead, it can create a negative room pressure that draws odors from the black tank. If you have more than one ceiling vent fan operating in the camper, it doubles the possibility of this happening. Lastly there is always a possibility of a manufacturing defect.

[NH_Bulldog]

The 320 toilet is ceramic and nothing at all like the 300 toilet which is plastic and is known to have some issues.

If you are getting an odor when flushing, it is likely a tank issue, not a toilet issue.

[JRTJH]

Changing from Thetford to Dometic means changing the floor flange and using a new toilet base ring (foam seal). If the flange wasn't installed "air tight" or if the foam seal "rolled or slipped" that may account for the odor.

Since you say it happens "when flushing" and not "when sitting unused", I'd guess it's something to do with the black tank odor coming up into the coach. I'd first make sure there's no vent or exhaust fan open and the air conditioner isn't running "directly forward of the vent stack or the bathroom roof vent... An exhaust fan running would "suck odor up the toilet when flushing" and an air conditioner "hot exhaust blowing past the vent stack or the open roof vent would pull odors up the vent stack and the venturi effect would push those odors down the vent and into the room.

[firestation12]

Originally Posted by JRTJH

Changing from Thetford to Dometic means changing the floor flange and using a new toilet base ring (foam seal). If the flange wasn't installed "air tight" or if the foam seal "rolled or slipped" that may account for the odor.

Since you say it happens "when flushing" and not "when sitting unused", I'd guess it's something to do with the black tank odor coming up into the coach. I'd first make sure there's no vent or exhaust fan open and the air conditioner isn't running "directly forward of the vent stack or the bathroom roof vent... An exhaust fan running would "suck odor up the toilet when flushing" and an air conditioner "hot exhaust blowing past the vent stack or the open roof vent would pull odors up the vent stack and the venturi effect would push those odors down the vent and into the room.

JRTJH’s post made me think of another source of camper air imbalance (negative pressure) that could draw black tank odors into the bathroom when the flush pedal is depressed…..a portable a/c unit that employs a single tube exhaust. These portable units displace about 400 cubic feet of air per minute. If you have one of these operating, consider it’s effect as a possible contributor.