Relative Durability of MSD Portpottie Models ?

Mar 20, 2015
3,094
C&C 30 Mk1 Winnipeg
Due to a recent thread by @AaronD about putting a MSD pumpout style portapottie in his Catalina, I been looking into what is available out there for a 5 gallon unit.

Looking a bunch of threads the options for seem to be:
Sanipottie 965 MSD
Sanipottie 975 MSD
Thetford, the 550P MSD

(Sealand has the 711-M28, but I exclude that becuase it won't fit on my boat and is too expensive for using in a small boat IMO)

Looking at recent reviews of the two Dometic Sanipottie models, the reviews seemed to be very mixed.

1) The 970 series has a a plastic rod for the flush system, and based on reviews, is prone to breaking.

2) The 960 series:
simpler than 975 (usually a good thing) and has a stainless steel metal flush rod.
Unfortunately some reviews complain of tank seam failure/leaks, and @$tingy_sailor reports bellows pump failure over a short time on his blog.
My current old Sealand unit has been reliable, and it's bellows are old but still work fine. I wonder if quality has slipped since Dometic took over ?

3)The Thetford 550P MSD seems to have better reviews than the Sanipottie units, but has recently been discontinued. It looks like the replacement model 365 may not support MSD functionality.

I find online store reviews are lacking, due to the fact that people always complain, but rarely bother posting positive reviews. (Not to mention that there is actually a, for profit, industry based on posting false reviews for some products)

Another problem is sample size... asking 2 people, or a single blog, for relability info is pointless.

I figure that asking the forum here may result in a slightly more accurate reliability reports.


So what say you ? Which one is more reliable ? Which one is crap ? (pun intended)
I don't want to deal with a broken system more than I have to.
 
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Dec 2, 1997
8,708
- - LIttle Rock
I'm not aware of any bad reviews of the Dometic 975MSD...which btw is an upgrade/replacement for the 960.
Although the Thetford 550P MSD has been discontinued, some retailers still have it in stock.
Both the Dometic and the Thetford have tank level indicators, which is a handy thing to have.
So go with the one YOU like best.
--Peggie
 
Mar 20, 2015
3,094
C&C 30 Mk1 Winnipeg
'm not aware of any bad reviews of the Dometic 975MSD
The same 976 unit without the MSD kit has a rating of 2.3 out of 19 reviews at WM.

"Nice design features, but cheap plastic materials and poor quality. I purchased 1 yr ago, water reservoir is leaking at the seams. I Do not recommend this product."

"Does not hold pressure as described. Flush handle flimsy. Seal between top and bottom tank difficult to set."

"This product only lasted 2 weeks with three uses and then the handle broke"

"The handle that opens the door to the holding tank easily falls out of it's groove. This is a less than fun job of reaching inside to push, with great difficulty, the gate back into the groove so that it can seal the tank back up (FYI, you have to take the toilet apart). It will not seal if you do not fix this and the smell will get out. YUCK! If they fix the tank valve arm, this would be a great head. But the cheap plastic rod and gate simply don't get the job done."



The 960 series had the following complaint on WM. I saw a similar complaint on one other site:

"I've bought two of these. I should have stopped at one. The holding tank on the first one split. Then the manual water tank pump failed. Then the second holding tank split in the same area as the first. They just can't handle tropical heat and torque stress."



But like I said, reviews can be misleading because you mainly see complaints in store reviews. Happy owners don't post comments years after buying it.

So with those complaints.. my thoughts were... "Were these units abused ? Were the owners too heavy to sit on them without damaging them ?"


Has anyone used the recent units for a while without issues ?

I'd be plesantly surprised to hear that Dometic makes the old sealand units to the same quality as before. Many companies cut corners on existing products. Especially when they buy out competitors and have less competition.
 
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Nov 22, 2011
1,192
Ericson 26-2 San Pedro, CA
I'm not aware of any bad reviews of the Dometic 975MSD...which btw is an upgrade/replacement for the 960.
Although the Thetford 550P MSD has been discontinued, some retailers still have it in stock.
Both the Dometic and the Thetford have tank level indicators, which is a handy thing to have.
So go with the one YOU like best.
--Peggie
Has the 550P been replaced with a model that has the same footprint? I've had mine since 2012 and it's been perfect. But I had a custom bracket made for it and if I ever did have to replace it, it would be nice if there was a model that would just drop in.
 
Mar 20, 2015
3,094
C&C 30 Mk1 Winnipeg
Has the 550P been replaced with a model that has the same footprint?
The Thetford 365 https://www.thetford.com/product/porta-potti-365/ which is listed by thetford as the replacement, is very similar to 550. No MSD functionality is listed though. I have emailed them for confirmation of that, and if they have any options vis-a-vis using 550 MSD parts on the 365, or a future kit being available.
 
Last edited:
Dec 2, 1997
8,708
- - LIttle Rock
Has the 550P been replaced with a model that has the same footprint? I've had mine since 2012 and it's been perfect. But I had a custom bracket made for it and if I ever did have to replace it, it would be nice if there was a model that would just drop in.
If I were you I'd buy another one to keep as a "spare" while it's still available. Since it would be likely to sit for quite a while, you'd want to lube the bellows (if there is one) and any other "rubber" bits annually to prevent 'em from drying out and cracking.
--Peggie
 
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AaronD

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Aug 10, 2014
723
Catalina 22 9874 Newberg, OR / Olympia, WA
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Nov 22, 2011
1,192
Ericson 26-2 San Pedro, CA
If I were you I'd buy another one to keep as a "spare" while it's still available. Since it would be likely to sit for quite a while, you'd want to lube the bellows (if there is one) and any other "rubber" bits annually to prevent 'em from drying out and cracking.
--Peggie
Thank you for your suggestion, Peggie. I think I'd like to do this.

Regarding maintenance: I've always maintained the pumps on my previous Groco and Jabsco heads using a dollop of SuperLube, but on my 550P I've not maintained or lubed anything on it as it is not obvious to me what there is to lube or how I would go about it. There are no bellows; I assume it is a pump with some kind of piston, but it's not obvious how to take it apart. Thanks.
 
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Nov 22, 2011
1,192
Ericson 26-2 San Pedro, CA
The Thetford 365 https://www.thetford.com/product/porta-potti-365/ which is listed by thetford as the replacement, is very similar to 550. No MSD functionality is listed though. I have emailed them for confirmation of that, and if they have any options vis-a-vis using 550 MSD parts on the 365, or a future kit being available.
Thanks. Please report back with Thetford's reply.
 
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Mar 20, 2015
3,094
C&C 30 Mk1 Winnipeg
the various options differ somewhat in height, which matters at least to us old-design C-22 folk.
Definitely something to keep in mind depending on the boat.

That is espeicially why the Sealand 771 M28 is not really an option.
Would be great if you have room and can justify the price.

What I like about the MSD Potties is the low water usage working well with a 5 gallon tank. They're kinda like a normal head without a lot of the hassles, including storage tank size, and can fit where the oem "cash and carry" units were.

In fact the Sealand unit our boat came with, would likely be able to mount to the 965 MSD tank, thereby converting it. I assume it needs longer brackets for mounting, even if the tank would fit.
 
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Dec 2, 1997
8,708
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All the 5.5 gallon portapotties--portable and MSD versions--are the same height. Same is true for all the 2.5 gallon potties. The footprints vary slightly by mfr, but is the same for both sizes. However, footprints from the same mfr can change just enough over the years to be annoying as mfrs update them, so the mounting brackets for your current old SeaLand may or may not fit a new Dometic
Why would you want a 965? It's actually a portable that offers"optional" MSD fittings. The 975 is the current MSD version.
And btw...even if the 7-11 M28 would fit, there's another consideration you may have overlooked: flush water is supplied by the boat's fresh water system, same as electric toilets that are designed to use fresh water.
--Peggie
 
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Sep 30, 2013
3,538
1988 Catalina 22 North Florida
Looking a bunch of threads the options for seem to be:
Sanipottie 965 MSD
Sanipottie 975 MSD
Thetford, the 550P MSD
Our 550P has been great for four years, but I'm done with Thetford until they offer a secure hold down bracket.

If I needed a new potty today, I would replace our 550P with a Dometic (Sanipottie) 965 MSD.

I see the 975's pushbutton flush as several added layers of complexity, and several additional potential points of failure. It uses an air pump to pressurize the freshwater tank, thus enabling the pushbutton flush. No thanks.
 
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Mar 20, 2015
3,094
C&C 30 Mk1 Winnipeg
Why would you want a 965? It's actually a portable that offers"optional" MSD fittings. The 975 is the current MSD version.
I see the 975's pushbutton flush as several added layers of complexity, and several additional potential points of failure.
My thoughts align with Gene.

New doesn't necessarily equal better.
In fact, I regularly advise customers to avoid new automotive designs, until they have been in use for a few years. Manufacturers design products to meet a marketing need, while maximising profit. Unfortunately that often results in unreliable or short life products. (especially when there is limited competition in a market)

My 1970's washing machine still works like new, and is repairable, when a new one barely last 6 years and is usually not worth repairing. I don't need fancy electronics to simply wash clothes.
My 30 year old Sealand Sanipottie is still in use.

For you Catalina 22 owners... to clarify what @AaronD mentioned:
Sealand 965 15-1/2" Height
Sealand 975 15 1/4" Height
Thetford 550P 16 1/2" Height

That 1 inch difference means the Thetford 550P won't fit under the V-berth cushions of a C22 if you are still using them.
Not sure if that may be an issue with other small boats, but keep that in mind. Like anything in a boat... check your measurements.
 
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Sep 30, 2013
3,538
1988 Catalina 22 North Florida
My 1970's washing machine still works like new, and is repairable, when a new one barely last 6 years and is usually not worth repairing. I don't need fancy electronics to simply wash clothes.
You're singin' my song, brother. I'd pay a ridiculous about of money for a 70's washing machine in good condition. Ditto for a 70's gas stove.
Remember Honda's TV commercial jingle "Honnnda, we make it sim-ple!" What the hell happened to the manifest knowledge that simplicity was a desirable attribute?
 
Mar 20, 2015
3,094
C&C 30 Mk1 Winnipeg
What the hell happened to the manifest knowledge that simplicity was a desirable attribute?
It cuts into profit. Customers ask same thing when they bring in a Chev Malibu, Mid 2000's Equinox, or a Cadillac and the labour to replace a headlight exceeds 2 hours, and requires bumper removal.

As for a good gas stove... the only option I see today is something like a Bluestar, or similar. Appliances meant for commercial use are usually simple and designed for long use.
 
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Dec 2, 1997
8,708
- - LIttle Rock
That 1 inch difference means the Thetford 550P won't fit under the V-berth cushions of a C22 if you are still using them.
Some people have solved that problem by removing the lid, allowing the cushion to be the "lid." The bowl is always empty except when in use and dome in the bottom of it seals the tank.
Remember Honda's TV commercial jingle "Honnnda, we make it sim-ple!"
Or Zenith tv and sound equipment's slogan "The quality goes in before the name goes on."
I was forced to replace my washer and dryer last year when a new motor for my 16 yr old dryer would have cost me half the price of a new pair. I HATE both of them! Among other reasons, the washer twists sheets into a tangled mess and the dryer rolls 'em into a ball. I should have known better than to buy GE.
--Peggie