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Discussion Starter · #1 · (Edited)
A couple folks had asked me to let them know how things went once I started installing the head listed above on my P26. Here's some things gleaned from my day yesterday that may be useful.

The 550P MSD version, instead of the usual pour-out spout that comes with regular porta-potties, has an barbed 1 1/2" pumpout fitting and a barbed 5/8" vent hose fitting instead. Both are located on the same bayonet-fitted cap that is attach to the rear right of the holding tank portion of the device. The pumpout fitting fits the hose fine, nice and tight, but the 5/8" vent fitting is very loose.. so loose I thought it might be 1/2", but that was WAY too tight so I went w/ 5/8" hose and just clamped it down. No worries there.. other than that a 3/4" or 1" sized vent would have been better. I'm going to try it stock for a while and see how it goes, then maybe modify it to a larger fitting if necessary.

On my Pearson, the location of the original standard Wilcox-Crittendon HeadMate was on a raised lip to port just aft of the v-berth. This raised lip is not large enough for the footprint of the 550P MSD (or any other porta-potty type of device that I've seen), so I had to fabricate (make template, ruin template, make bad language sounds, make another template, trace template on marine plywood, cut plywood, realize that one cut out was made on the wrong side, make more bad language sounds, set cut plywood in place on boat, discover that wrong side had been sanded, make more bad language sounds, discover that plywood fits so poorly that I could have done a better job ignoring the template and just chewing the board to an approximate shape with my teeth by eye, etc... or, in other words, "fabricate") a platform to support it.

I filled the three holes left from the original head mounting with epoxy; the plywood core had rotted around the lag bolts, but not far at all. I couldn't get an awl into the wood at an angle because it was still so solid, so at this point I just filled'em up and called it good. Down the road a ways, who knows...

I put the "fabricated" 1/2" plywood support plate over the original head location, and cut a support for the front where it overhangs the original lip. Thetford includes a template for the two mounting brackets, and getting those screwed into the plywood in their correct positions is a snap.

The two admittedly cheap-feeling plastic mounting bracket/clips seem to do a good job holding down the 550P, but there's a caveat. The hose I bought from West Marine (I chose from their huge selection of the one 1 1/2" sanitation hose they had in stock) was very stiff, and I couldn't get it to approach the head at an angle that the fitting on the head liked. The pressure of the the hose trying to make the bend was enough to make the head bend out of it's brackets. After some more magic incantations and 20 minutes of sweating out sustaining life fluids, I did manage to get the hose, the head, and the mounting brackets to "play nice together," but there's still more pressure on the brackets and fittings than I'd like. I think I'm going to order some of the Raritan SaniFlex hose... assuming I can get the current "What We Have In Stock" hose off again.

I still have to install the vent thru-hull. It'll be my first time cutting a hole in my hull, so I'm already a bit nervous about it. According to Peggy Hall's book, the vent line should run as horizontal as possible. Well, that's not possible. Would it be better to run it vertically about 2.5', or zig zag it so it's like a sideways "V" over that distance? My rub rail is about 8" below the top of my deck. Should the vent be mounted below the rub rail? How far? I bought a basic "mushroom" vent.. is that OK?

As far as the head itself goes, it should be fine. Pluses - no holding tank, much gained interior storage for other things, less plumbing, no through-hull intake needed, and, according to the literature, good for 60 uses before pumpout is necessary. I'll be happy if it's even half that. Negatives.. well, it's plastic and feels like it, and the vent based on Peggy's book, conversations with her, and virtually every OTHER recommendation I've ever read on Sailnet, is too small. Other than that, none yet. I'll keep you posted.

Any advice is ALWAYS joyfully received. If I can answer any other questions about the 550, let me know.

Best to all,

Barry
 
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Interesting read. I'm thinking about doing the same thing. We're lake cruisers and will NEVER be on our boat for more than 3 days, and we'll always be within a few hours of a pumpout. Our favorite anchorage even has an outhouse on shore...and while I've never done it, I think my kids just pee in the lake while they're swimming.

I don't see the value of maintaining a full head with all the accouterments and exciting maintenance opportunities that they offer.

So do you have the dump-out option also or is it pump out only?
 

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Discussion Starter · #3 · (Edited)
So do you have the dump-out option also or is it pump out only?
The MSD version comes with the cap that has the 1.5" and 5/8" fittings embedded in it for "permanent" installations, and a sealed solid cap that can replace the cap with the fittings. It does not have a "pour-out" cap. I find it hard to believe that the pour-out cap included with the regular 550P without the "MSD" ("Marine Sanitation Device") designation wouldn't fit, but I've called Thetford to find out and they said that the bases are different and that the parts are not interchangeable. Given usual manufacturing processes, it just doesn't make sense to set up a manufacturing line for two different bases when the rest of the product is the same, so I think it may be more of a "CYA" policy that the rep was feeding me since the MSD devices are meant for permanent installs and meet the Canadian regs for permanent sanitation devices. I don't know for sure.

Here's their parts diagram:

http://www.thetford.com/HOME/PARTS/PortableToilets/PortaPotti550ModelsParts/tabid/902/Default.aspx

Note that the cap with the fittings, item #7 part #92924 states that it only fits the MSD model, but that the pour out spout cap, item #5, part #92907 does NOT say "does not fit MSD version" or anything like that. Who knows.

Short answer.. no, the MSD doesn't come with a pour-out spout, and supposedly one is not available for it. You can easily remove the cap with the fittings, recap the holding tank with the included solid cap, and take the capped tank off the boat all within a matter of seconds. Dumping it might not be as pretty as it would be with a pour-out spout, however... :p

It might be worth buying the pour-out spout cap just to see if it DOES fit. My money says it probably will, contrary to the company line. That's pure conjecture, of course.

Barry
 

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I'm thinking about doing this conversion from a fixed head and holding tank on my Tartan 30 for the same benefits as what you had listed. I also have the raised lip where the old head rested and would have to fabricate something to make the floor level.

I'm curious about how this has worked out for you, and if you have any advice for someone considering this.
 
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