Affordable Alternatives to Replacing a Dometic 320 RV Toilet
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Thread Summary
Original Member Title: Replacing toilet
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Members discussed options for replacing a Dometic 320 toilet, focusing on cost-effective alternatives for full-time RV living. The original poster sought less expensive suggestions after the flush ball cracked, noting that the ball is not replaceable in the 300 series. Several RVers clarified that while some parts can be replaced, a cracked ball typically requires a full unit replacement.
The conversation highlighted that Dometic has discontinued the 3nn series, with the 4nn series (400...
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The conversation highlighted that Dometic has discontinued the 3nn series, with the 4nn series (400...
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What is wrong? I don't think they can wear out.
Carl n Susan
Senior Member
Site Team
RV LIFE Pro
Dometic has discontinued the 3nn toilet series and replaced them with the 4nn series. There is a 400 and 410 (akin to the 3nn) series, but the 420 model is not yet available (when I last checked). Not cheap, but the 320 was my toilet of choice and I am hoping the 420 replacement is available in the future.
They do wear out. The seal between the bowl and the base or the springs that hold the flush ball tight are the most common reasons for replacement. I had to replace my 320 two weeks ago. Fortunately I found a RV parts place that had stocked up on them.
They do wear out. The seal between the bowl and the base or the springs that hold the flush ball tight are the most common reasons for replacement. I had to replace my 320 two weeks ago. Fortunately I found a RV parts place that had stocked up on them.
Ball is cracked.
CNCAPP
New Member
Carl n Susan
Senior Member
Site Team
RV LIFE Pro
Nope, it specifically says it doesn't fit the 3nn Dometic series toilets.
Carl n Susan
Senior Member
Site Team
RV LIFE Pro
I only have had two kinds of RV toilets: the original Thetford Montana uses and the Dometic 320. After the Thetford flooded the floor for the second time (I am a slow learner), it was replaced by the Dometic. There are lots of stories on the MOC about the Thetford and its propensity to overflow the bowl and flood the surrounding area. I would stay away from it.
Have you considered Lippert Flow Max?
www.lippert.com
Flow Max™ RV Toilet - White Round Plastic Bowl #2024030310 | Lippert
With powerful flushing capabilities and a residential seat size for ultimate comfort, the Flow Max RV toilet offers the best features of a household toilet with a design specifically built for your rig.
www.lippert.com
JON SUSN
Advanced Member
RV LIFE Pro
Sometimes I have to get smacked upside the head twice to get it right also…..LOL
Todd & Mary
Senior Member
RV LIFE Pro
In my opinion the 320 it is a better unit. The flomax is ALL plastic, so you would have to be careful cleaning it so it doesn't get scratched.
Really like the 320, but been waiting for Dometic to address some of the occasional issues noted with the 320. They said the release date for the 420 is suppose to be April fools day, so 
Improvements:
The Dometic 400-series, including the 420, improves on earlier designs by combining a more compact installation footprint, a redesigned structure for durability and easier cleaning with internal durability and odor-control changes. The most noticeable upgrade is the short 7.625-inch rough-in, allowing a full elongated porcelain residential-style bowl to fit in tighter RV bathrooms where many previous elongated models could not. The series also adds chair-height seating, a soft-close seat, and a refined 360-degree “PowerFlush” rim rinse for better bowl cleaning. Internally, the design appears to move toward a more integrated, sealed bowl-to-base structure, reducing the chance of waste entering hidden cavities between shells—a problem that caused persistent odor issues in some earlier RV toilets. Combined with improved flush-ball sealing and updated valve components, the 400-series keeps the familiar gravity-flush, foot-pedal system but focuses on better fit, improved reliability, and stronger odor containment.
Improvements:
The Dometic 400-series, including the 420, improves on earlier designs by combining a more compact installation footprint, a redesigned structure for durability and easier cleaning with internal durability and odor-control changes. The most noticeable upgrade is the short 7.625-inch rough-in, allowing a full elongated porcelain residential-style bowl to fit in tighter RV bathrooms where many previous elongated models could not. The series also adds chair-height seating, a soft-close seat, and a refined 360-degree “PowerFlush” rim rinse for better bowl cleaning. Internally, the design appears to move toward a more integrated, sealed bowl-to-base structure, reducing the chance of waste entering hidden cavities between shells—a problem that caused persistent odor issues in some earlier RV toilets. Combined with improved flush-ball sealing and updated valve components, the 400-series keeps the familiar gravity-flush, foot-pedal system but focuses on better fit, improved reliability, and stronger odor containment.
Last edited:
I replaced my damaged 320 Dometic toilet, with a 410. All the parts are serviceable and it's a great fit. Thanks for all your attention.
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