Installing a MSD potty in our C22

[Gene Neill]

Looks like this is finally happening. I've bought the potty, and now I've started this thread. So there's no turning back!

I was on the fence between using the Dometic 965 MSD and the Thetford 550P MSD. We had years of experience with the Thetford, and were completely satisfied except for Thetford's idiotic hold down bracket. I had a slow-burning resentment toward Thetford over this, so I purchased the Dometic unit and we used it for five days over this Christmas, in non-MSD fashion, removing the tank and dumping it remotely at the end of the cruise. The Dometic, I will say, has excellent hold down brackets.

But we both disliked the Dometic rather strongly. Compared to the Thetford, it is cheaply and crudely made. The bellows-style flush pump is cheesy and awkward. Ditto the handle that dumps the bowl into the tank. Worse, when you need to pump some water into the bowl in preparation for a major contribution ... you can't. 80% of the water in the bowl almost instantly leaks out of the bowl and into the tank. Then things get messy.

Worst of all, it just isn't plumbed right for this particular boat. The MSD plumbing fittings (and this part is not a knock on Dometic, just bad luck) just aren't in the right place, or angled correctly, for a new design C22. They happen to be just right on the Thetford.

So, Thetford it is, because I'm not aware of an option three. And the Admiral is done experimenting.

Link to the Thetford 550P MSD. More drivel to follow. And questions. I have LOTS of questions!

Amazon.com

 

[Gene Neill]

Just thinking out loud here. I need to order some sanitation hose to go from the potty to the Y pipe. And from there to the deck pumpout, and to the overboard discharge.

I need some vent hose, too.

And a Y-valve.

And a deck fill fitting.

And a deck vent fitting (does it need to be the deck, necessarily? A certain level above the heeled waterline?)

And a manual waste pump.

Oh, and I need to pull the Thetford potty out of the box and start looking at how exactly to fabricate a hold down bracket for it. I'm envisioning some sort of welded aluminum version of the sorry little plastic brackets Thetford sells.

The fittings built into the potty will determine the hose diameters I need, so I'll look at that in the morning. And I'll look at the SBO store first for all these items.

 

[Alan Gomes]

Looks like this is finally happening. I've bought the potty, and now I've started this thread. So there's no turning back!

I was on the fence between using the Dometic 965 MSD and the Thetford 550P MSD. We had years of experience with the Thetford, and were completely satisfied except for Thetford's idiotic hold down bracket. I had a slow-burning resentment toward Thetford over this, so I purchased the Dometic unit and we used it for five days over this Christmas, in non-MSD fashion, removing the tank and dumping it remotely at the end of the cruise. The Dometic, I will say, has excellent hold down brackets.

But we both disliked the Dometic rather strongly. Compared to the Thetford, it is cheaply and crudely made. The flush pump is cheesy and awkward. Ditto the handle that dumps the bowl into the tank. Worse, when you need to pump some water into the bowl in preparation for a major contribution ... you can't. 80% of the water in the bowl almost instantly leaks out of the bowl and into the tank. Then things get messy.

Worst of all, it just isn't plumbed right for this particular boat. The MSD plumbing fittings (and this part is not a knock on Dometic, just bad luck) just aren't in the right place, or angled correctly, for a new design C22. They happen to be just right on the Thetford.

So, Thetford it is, because I'm not aware of an option three. And the Admiral is done experimenting.

Link to the Thetford 550P MSD. More drivel to follow. And questions. I have LOTS of questions!

Amazon.com

I have the Thetford 550P. Although it's a discontinued model they are still out there, as the link you provided shows. The brackets do indeed suck. I immediately tossed them and had some brackets fabricated out of meta,l and it's worked out just fine.

 

[Alan Gomes]

I have the Thetford 550P. Although it's a discontinued model they are still out there, as the link you provided shows. The brackets do indeed suck. I immediately tossed them and had some brackets fabricated out of meta,l and it's worked out just fine.

If you'd like to see a few pictures of my installation I had posted them in a thread about this on the Ericson Owner's site.

 

[Gene Neill]

I have the Thetford 550P. Although it's a discontinued model they are still out there, as the link you provided shows.

Thetford has been saying the 550P was discontinued for YEARS, and yet they have always been out there for sale. I don't know what to make of it. But I may pick up a second one and throw it in storage against the day this one breaks and has become irreplaceable.

By the way, I misspoke about being unaware of any third-option potty. There is still the Dometic 975MSD which looks like a quality unit. But I am put off by their pressurized push-button flush system, which is neat but adds an unnecessary level of complexity.

There is also the Visa Marine Potty MSD18L. All I know about that one is that it exists.

 

[dlochner]

And a deck vent fitting (does it need to be the deck, necessarily? A certain level above the heeled waterline?)

It will be easier to use if the fitting is on the deck. In most pump outs it is necessary to hold the pump nozzle on the fitting which is flush with the deck. In this case gravity works with you not against.

For hose use Saniflex. Easy to work with as it is bendable and guaranteed odor free for 10 years. Do not use cheap hardware store vinyl for the vent hose, it will odor permeate in a few days.

 

[Peggie Hall HeadMistress]

I agree with everything Dave said.

I'm also very curious to know more about the Visa MSD portapotty 'cuz I'm seeing an increasing number of complaints about the quality of the Dometic 965--not the only formerly SeaLand product that's no longer the same quality--so I'll no longer reommend it. We definitely need a new alternative to the Thetford. I went to the site and saw that it's a Canadian product that's apparently sold in the US too...Americans will a need some basic knowledge of how to convert liters to gallons to read the level indicator. Photo shows a pumpout fitting, but doesn't show a vent fitting...I'll ask about that when I call them next week.

--Peggie

 

[Sail22Capri22]

I installed the Thetford 550p in my Capri a year ago. It worked great this past season. I installed the sanitation hose to the deck and vent just under that. I am very pleased with the toilets operation and ease of pumping out. I am lucky my Capri had a small indentation in the floor to allow the Potti to sit in the spot and I have not needed to add anything else to secure it.

 

[Gene Neill]

It will be easier to use if the fitting is on the deck. In most pump outs it is necessary to hold the pump nozzle on the fitting which is flush with the deck. In this case gravity works with you not against.

Yes, definitely on deck for the pumpout fitting. It's the vent fitting I was unsure about.

 

[LakeShark]

Yes, definitely on deck for the pumpout fitting. It's the vent fitting I was unsure about.

My new design came with a plumbed MSD that I have since discontinued the use of. The vent fitting is in the side of the hull below the rub rail and the pump out was in the deck.


The reason I discontinued it was because I disliked the hoses running up along the wall and since I trailer everywhere it’s just as easy to disconnect and make the walk of shame. Currently we use the V-berth for sleeping (I know you use yours for storage but we have 5 on board) and I have swapped over to the Dometic 975MSD. Been 4 or more years now with it and it works great. The 5 gal size easily makes it though 7 or more days of sailing with all 5 onboard. Generally the head is though reserved for more complicated visits if you know what I mean. The push button is no big issue and seems to control water better than just having kids continually pump to "clean" out the bowl. Also, the 5 gal model has great brackets and fits just under the berth insert. No smells either but I have never hooked up the MSD portion.

I can say that the head has taken a full knockdown to port with no issues or leakage. When I say knock down, I mean sails in the water, Spreader tips submerged, wing keel and rudder out of the water, and water pouring over the cockpit coaming into at an alarming rate (enough to sink the boat if it got in the cabin door. It's a wild ride for sure when it happens but once the boat is back up and the water drains out the scuppers in the stern it’s nice to know I am not mopping up the interior while holding my nose if you know what I mean. I hope this helps.


Oh, and for hold down brackets why not make something that can be 3D printed. You may find a prototype you like that you can then have made from something more robust.

 

[LakeShark]

@Gene Neill In this picture you can see the vent fitting and Pump out fittings. Never mind the relaxed racing crew we were waiting for wind and enjoying our day win the water last year in Arkansas.

The vent fitting is the white through hole on the side in the red stripe. The pump put fitting is near the center stay in the side deck on the top. For a vent fitting I would recommend using a proper vented cap and not a though hole to prevent water egress and mud dobbers from setting up residence. Currently with no hose mine is filled with silicone from the inside.

 

[AaronD]

@Gene Neill : My own parts list is at Sailing and restoring #9874 (and some additional pictures in an earlier post on the same page).

I selected the 2 hoses based on Practical Sailor smell-penetration testing (@thinwater ran those tests, if I recall correctly). I picked the most flexible hoses in each size of the ones that worked well in their tests.

 

[Project_Mayhem]

I have the Dometic 965. The bellow leaks and the flush only rinses part of the bowl. I cut some slits in a piece of tubing and attached it to the nozzle for more even coverage. There's a four page long thread regarding my current and previous (975) heads, modification, installation and preferred treatment options. Note that you may need to add more treatment than a traditional head

Looking for recommendations for Porta Pottie with MSD

 

[Gene Neill]

@LakeShark That is a great endorsement of the Dometic 975! It appears to have nothing in common with the Dometic 965 other than it's name.

I have decided to use GRP to make a bracket for the 550P, rather than welded aluminum. I already have a 12"x12" piece of 1/4" sheet to work with so the hold down bracket is as good as done.

 

[Project_Mayhem]

My 975 leaked if filled too much and the level gauge stopped working. It also stopped pumping water but that may have been due to the use of lake water. Good looking head, complicated for guests but broke in multiple ways. After emptying the waste tank I placed it next to the dumpster in the marina. To my surprise someone had taken it by the next day. I bet you they were in for a surprise!

 

[Gene Neill]

@Gene Neill : My own parts list is at Sailing and restoring #9874 (and some additional pictures in an earlier post on the same page).

I selected the 2 hoses based on Practical Sailor smell-penetration testing (@thinwater ran those tests, if I recall correctly). I picked the most flexible hoses in each size of the ones that worked well in their tests.

I assume you went out through the hull with your vent, as opposed to out through the deck?

In your thread you mention "Sani-Fresh" hose, I assume you meant Sani-Flex? @Peggie Hall HeadMistress has endorsed Sani-Flex as her favorite, so that's what I ordered earlier today. Well, her endorsement and the fact it is supposedly the most flexible, which I think is going to be important. There was a little sticker shock when I saw my total with tax and shipping. The best price I could find was $16.80/foot at Fisheries Supply.

 

[dlochner]

Yikes, usually Fisheries has decent prices. Unfortunately, Defender has a much lower price. Perhaps you can cancel your Fisheries order if they haven't cut the hose yet.

Raritan Sani/Flex Sanitation Hose

Raritan Sani/Flex Hose is the most flexible marine grade hose on the market. Features: Odor free Smooth inside wall surface allows for a greater fit and seal during installation Extremely flexible for easy installation Low bend radius up

defender.com

 

[Peggie Hall HeadMistress]

. For a vent fitting I would recommend using a proper vented cap and not a though hole to prevent water egress and mud dobbers from setting up residence.

The "proper" vent thru-hull is designed to keep sea water out of fuel and water tanks. Boat builders us the same thru-hull for all vents because it costs them less to buy one kind in bulk than doing it correctly, totally ignoring the fact that they're unsuitable for waste tank vent thru-hulls because, unlike water and fuel tanks, waste tanks need to breathe...oxygen prevents odor from being created in them. A "proper" vent thru-hull doesn't allow that, an open thru-hull does...and unlike a fuel or water tank, the small amount of water that might get into the holding tank when the boat is heeled doesn't matter. As for preventing vent blockages. that's easy: put a hose nozzle against an open thru-hull to backflush the vent line every time you wash the boat and/or pump out. Anything that's tried to set up housekeeping in the vent line will just get a waterslide ride into the tank.

--Peggie

 

[Gene Neill]

Yikes, usually Fisheries has decent prices. Unfortunately, Defender has a much lower price. Perhaps you can cancel your Fisheries order if they haven't cut the hose yet.

Raritan Sani/Flex Sanitation Hose

Raritan Sani/Flex Hose is the most flexible marine grade hose on the market. Features: Odor free Smooth inside wall surface allows for a greater fit and seal during installation Extremely flexible for easy installation Low bend radius up

defender.com

Yeah, but Defender has a total of one foot of 1 1/2'' Sani-flex for sale right now. Just my luck.

I'm looking at the bright side. West Marine wants $21 a foot for it.

 

[Gene Neill]

A "proper" vent thru-hull doesn't allow that, an open thru-hull does...and unlike a fuel or water tank, the small amount of water that might get into the holding tank when the boat is heeled doesn't matter.
--Peggie

Thank you, this is good news.