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Old 06-27-2012, 10:47 AM
thewayneo thewayneo is offline
Join Date: May 2010
Location: Evergreen, Colorado. Halfway between Heaven and Paradise at 8,100 ft altitude.
Posts: 111
Default Installing a Sealand 711-M28C with 3" Gravity Discharge


This toilet was originally produced for marine applications and later adapted for RV use. The marine version has a 1-1/2” side discharge, the RV version has a 3” bottom drain. It is used in Scamp brand lightweight travel trailers. The Sealand toilet stores waste in a 9.5 gallon poly tank mounted on the floor of the TM and connects to the existing 3” toilet drain pipe and dump valve. It uses the existing water pump and water from the fresh water tank to flush. The Sealand manual recommends a 2-4 GPM pump, but they actually consider a 3 GPM pump to be the minimum. Here are links to: 1) Dometic/Sealand, 2) Owner's Manual, 3) Forum post “Replace Thetford w/ Sealand 711-M28C?”.

Additional info can be found by searching the forum for “thetford” and “sealand”.

Will it Fit My Model TM?

Maybe, but maybe not! The dimensions given in the Sealand literature are correct EXCEPT for the front-to-back tank measurement (unless they have corrected it). Front to back is actually 17”. So first you will need to measure the available space between your shower and vanity. Then look at your existing 3” toilet drain pipe under the floor and see if it could be moved 1-1/2” towards the front of the TM. Read the Owners Manual (above link). Pic 1 shows a Sealand toilet installed in a 2006 2619 TM.

Where to Order

Here are links to two possible sources to order from: $395 + shipping/tax. Scamp is in Minn. This is the toilet they put in their lightweight trailers, and the correct one for us. Note their website still calls it "Travelor". Apparently when Dometic bought Sealand, they said "no more names for our toilets!"

For folks on the west coast, ARDEMCO in Ca. sells it for approx $500+, but if you pick it up, you can save shipping costs.

The following info is based on only one installation, and only pertains to a 2006 2619. Also, this toilet was ordered from ARDEMCO and is slightly different from the one Scamp sells. As other TM owners install this toilet, hopefully they will add their experiences, improvements, and better methods to this.

Materials Needed to Install

These were all purchased at the big orange “Depot” place:

1. Ten foot length of 1/2” PEX flexible tube (I had 2-1/2 feet leftover).
2. Sharkbite fittings all 1/2”-- one tee, two 90 degree, one PEX-to-pipe thread.
3. Two 1-1/2” black ABS straight couplings, purchase a 2' length 1-1/2” ABS pipe.
4. 3” black ABS coupling, purchase a 2' length 3” ABS, 3” male thread/glue straight adapter for the bottom of the tank See pic 2.
5. ABS glue.
6. 6-foot length of flexible 5/8”ID, 7/8”OD vinyl hose for vent.
7. Purchase shorter screws that hold the tank down, if you don't need such long ones.

Tools Needed

In addition to common hand tools, these helped:

1. 5” long, fine tooth jig saw blade to enlarge the 3” hole in the TM floor.
2. Phillips screwdriver with 8” long shank to screw the holding tank to the TM floor.
3. A tool to cut tubing—I found that a “mini cutting wheel” cutter worked on the existing TM tubing but would not work on new PEX tubing (too rubbery). A Fein Multimaster oscillating tool works. A ratcheting PVC pipe/tubing cutter scissors from the Depot ($13) might be worth the investment and makes a very clean cut.
4. Jig saw, drill.
5. Small hole saws.


To remove the existing Thetford recirc toilet see this thread. Before removing the existing floor flange, cut the 3” drain pipe close to the floor with a Multimaster (or other cutting device) leaving enough pipe on the valve assembly to re-attach the whole valve assembly later. Also cut the 1-1/2” grey water pipe half way between the slide valve and 90 degree bend. This will leave enough to re-attach two straight couplings to compensate for the plumbing “moving” 1-1/2” towards the front of the TM. Pic 3 shows how two couplings add the needed 1-1/2”.

In general, installation involves mounting the tank and bowl, connecting a fresh water flush line and vent, and reconnecting the 3” drain pipe and 1-1/2” grey water drain pipe.

First, ensure that the TM is level, especially side-to-side. Clean the floor. Clean or spray paint any wall damage caused by the old 12-volt wire rubbing on the paint. Rust-Oleum Antique White 7794 was a good match. You might also paint the screw heads and washers on the screws that hold the tank to the floor, they show at the front of the tank.

Place the tank on the floor, centered in the space and 3/4” from the wall, mark the hole location. Mark the location of the four hold-down screws by hammering the end of the long screwdriver. I placed a 3” coupling over the marked hole, then traced the larger diameter, and cut a little bigger than that just to be sure. TM left a gap between the 3” pipe and the styrofoam in the floor, so I did too. Pre-drill the 4 screw holes. At this point, it might be a good idea to temporarily screw down the tank and attach the bowl. First make sure the screw holding the vacuum breaker cover is tight. To secure the tank to the floor, (especially the rear hidden screws) I held a washer on a 8” phillips screwdriver and let it slide off into place. Then with blue tape, loosely tape the screw head to the screwdriver and drive home, leaving the tape well attached to the screwdriver. Place a level on the bowl from front to back, side to side, and check for level. Level under the tank if not perfect. This toilet tries to use as little water as possible, and if the bowl is not level you won't get a good wash when flushed. For final assembly, you may wish to run a bead of caulk around the tank bottom.

Note where the flush water line attaches to the toilet and the best place to route the new line, and where the vent hose attaches, and where it might exit the floor, if that's where you choose to exit (suggested by the ARDEMCO installer). Pic 4 shows the vent hose through the vanity and shelf, exiting through the floor.

Tee into existing fresh water line for flush water. In may be easiest to do this under the kitchen sink. Pic 5 shows the tee under the kitchen sink. Sharbite/PEX fittings are handy in tight spaces, but other connectors could be used. PEX cuts need to be straight to seal correctly. You may wish to clean the inside of the cut pipe with a pocket knife so it will fit easier into the Sharkbite fitting. PEX tubing should not exert mis-aligned side pressure on the fitting, use 90 degree fittings. Before connecting the PEX-to-pipe thread fitting to the toilet, it might be a good idea to run some water into a bucket in case any debris entered the pipe while cutting/installing.

Drill holes for vent hose. Best to measure 3 or more times. For the floor, try a tiny long drill bit first just through the aluminum skin and probe with a bamboo skewer. Then drill through to see if you come out where you want. Then a hole saw to cut just through the aluminum skin. Then dig out the styrofoam by hand to make sure there's nothing important buried in there.

Re-connect the drain pipes. This will essentially put everything back the way it was, just 1-1/2” towards the front of the TM. Place teflon tape on the 3” male thread/glue straight coupling and screw into bottom of tank. Dry fit or measure a piece of 3” pipe and coupling that will allow the old drain assembly to hang at the proper height in relation to the grey water pipe drain. Also determine if two 1-1/2” couplings (with a stub of pipe between them) will be the right length to reconnect the grey water pipe. Make these connections. Fill the wallowed out 3” drain pipe hole in the floor with spray foam if needed.

Hopefully, other TM owners who install this toilet will add their experiences, improvements, and better methods here:

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Attached Files
File Type: pdf Dometic_SeaLand_711-M28_Toilet.pdf (472.7 KB, 1727 views)

2006 2619, with REAL Flush Toilet (Sealand), NEVER ANY HOOKUPS!!!
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