Dometic 420 Toilet Upgrade From 310

[klassic]

If you’re thinking about changing out a Dometic 310 for the newly released 420 elongated, it’s worth it.
Much better

 

[Carl n Susan]

What changed to make it much better?

 

[klassic]

1- elongate, more comfortable.
2- rim over the inner edge
3- slow close seat
4- leaky seal seat redesigned (not to leak)
5 - foot valve must be slightly redesigned, much quieter, and half press to fill works better.
6- they made the whole new 400 product line with a standard mounting depth of 7 5/8” so an elongated would probably fit where it wouldn’t before.

 

[Carl n Susan]

The leaky seal redesign is worth it all by itself (if it actually works).

 

[brenkco]

I hope the new seal design works. I installed a new 320 in November. It has yet to hold water!

 

[klassic]

I think you could get them to warranty it.
Call Dometic.
They know the 300 series has a problem, thus the new 400 line.

 

[brenkco]

Thanks!

 

[twindman]

Is the seal being talked about the one inside the bowl around the opening to the sewer? I have had a 320 for many years and replaced the seal once. I had to buy a pair and still have the 2nd one.

 

[Carl n Susan]

Yup, the seal inside the bowl is the one. The older ones seem to be ok (a familiar story), but the newer ones not so much. I replaced my 320 in January due it not holding water and two months later it is leaking again. My RV dealer told me there is a one year warranty on the toilet and Dometic will replace it. Hopefully for Ken (and others), with a new 420.

 

[brenkco]

That’s the one I’ve been having trouble with

 

[Carl n Susan]

That’s the one I’ve been having trouble with

I am assuming it was a 320 as the 420 wasn't available in November. I suspect they changed something in the spring return mechanism of the bowl valve on the 320. No amount of cleaning or plumber's grease helped.

 

[klassic]

I am assuming it was a 320 as the 420 wasn't available in November. I suspect they changed something in the spring return mechanism of the bowl valve on the 320. No amount of cleaning or plumber's grease helped.

Yes. I’m hoping the problem is actually fixed.
My new 310 that came in my new Montana, the seal lasted 2 months.

 

[Mikendebbie]

I got curious about what might be the difference in the seals for the 420 vs the 320…so I googled the manuals for both units, read and looked at the illustrations. Unfortunately the illustrations don’t show a cross section of either rubber seal to see if the new one (for example) has a double-triple super fin arrangement that presses against the ball better than the old rubber seal (note - I just made that up for illustration purposes).

Both manuals have a 3D drawing/sketch of the toilet with a black round seal at the bottom of the bowl. The verbiage to install the seal is similar for both. Both units have identical trouble shooting instructions for a leaky bowl.
…you see…the rubber seal has lost its shape and needs to be re-conditioned.
1. Open the ball and Clean the seal
2. Press down on the seal into the opening (so it will better engage the ball)
3. Release the ball
4. Pour 1 quart of hot tap water into the bowl and let it sit until it is cool.

Basically without closely examining the seals - I can’t really tell what is new or better…maybe a forum member can elaborate. My 4 yr old 320 leaks, but I will try the hot water trick maybe tomorrow.

 

[klassic]

I’m thinking perhaps they made the porcelain lip the seal attaches to a little better to stop leaks from that side.
And maybe made the “ball” (whatever the moving part is called) stay better pressed against the seal lip.
??

I know when the Dometic customer service techs were trying to diagnose my leaking seal they wanted the ball deflection checked.
And then they said do the hot water trick.
I think they sent me a diagnostic pdf.

 

[klassic]

But anyway, I wanted an elongated and I was glad to ditch the 310 and try out the new 400 series

 

[brenkco]

I am assuming it was a 320 as the 420 wasn't available in November. I suspect they changed something in the spring return mechanism of the bowl valve on the 320. No amount of cleaning or plumber's grease helped.

Correct. That has been my experience too. Hopefully dometic will step up!

 

[Spartacus]

Okay, I'm going to have to look into that, I replaced the 320 a few years ago. So what the price of the new one?

 

[Mikendebbie]

Dometic 420 from Amazon…see screen shot below.
I think I paid $299 for my 320 in 2021 from PPL RV (online) out of Houston…best price I could find at the time.