Dometic 711-M28 Gravity Toilet - opinions?

[Nick F]

Hi - I am planning to completely renew my 2 toilets/holding tanks and saw a post of Peggy's that mentioned this self-contained toilet. Can anybody give me feedback on actual experience with this unit? It looks like a really interesting option.
Thanks,
Nick

 

[Shrew]

IMHO this looks like it was designed to replace porta potties with a self-contained head and holding tank combo. To me this looks like the intention was upgrading smaller pocket cruisers, walkarounds and center consoles with a porta pottie in the console.

I wouldn't consider this suitable for a cruising boat.

Holding tank capacity . . . . . . . . . . 9.5 Gal. (36L)

A number of years ago I had a holding tank failure. I ordered a tank, but it was on back-order. To get through the month of July and my vacation I installed a 10 gallon tank from Todd Industries I got from either WM or Defender.

The 10 gallon tank worked fine, however we found that we averaged 6 gallons a day with a manual pump flush. This meant, when out we had to get daily pumpouts to be safe. That is very cumbersome.

https://www.dometic.com/assets/47/36/installation and operating manual_64736.pdf

 

[HeadMistress]

It was a very popular toilet on boats in the 30-40' range that didn't really have a good location for a holding tank. I knew several people who'd had one for years and loved it...and it's always been one of my favorite systems for a bunch of reasons:

It needs no power...no plumbing except the vent line and pumout line. Requires almost -0- maintenance...just rinse the tank after every pumpout--which you can do with a hose or a bucket via the hole in the bottom of the bowl...and keep the bowl clean. No pump or other moving parts...in fact the ONLY parts are the water valve and the flush control (which btw is the same one used on VacuFlush). Unlike VacuFlush, it really CAN use as a little as a pint of water! Uses the same tank product(s) as any other tank and requires venting, same as any other tank. Keep the vent line short and straight, which may require installing a new vent thru-hull if the existing tank vent is more than 5-6' away from it...and would be a good idea to use an open bulkhead thru-hull instead of a "vent" thru-hull, same as you would for any other tank if you want to prevent odor and vent blockages.

Oh...I also love the price. SeaLand Traveler at Defender (I really should update my bookmark to change "SeaLand" to "Dometic"...but as long as it continues to work....)

--Peggie

 

[Nick F]

Thanks Shrew - I am thinking of starting with the self-contained 2 x 9 gal and later adding a holding tank to which I can transfer the toilet contents to extend range.
The advantages I imagine with this toilet:
- totally silent in use (I get up during the night!).
- with a macerator pump I can transfer further than the normal 6ft distance limit, so I could get away with only 1 holding tank.
- it requires very little flush water, so the 9 gal actually lasts longer than if it were fed by a manual toilet.

More comments, please. Who actually has one of these units?
Nick

 

[Nick F]

Thanks Peggie - you posted while I was typing!

 

[boomerang]

We have one of those heads in our boat. Peggy, you so kindly helped me to rethink my attitude towards the self-contained unit. In another thread you correctly pointed out that it's 9 gallon capacity was more than adequate in most circumstances due to the fact that it uses so very little water with each flush. You also helped me realize that any odor issue we had could be better controlled with proper venting as stated above and a environment-friendly additive. Our 2021 season will have an upgraded venting system on the tank.
So Nick, contrary to my earlier posts not being completely enamored with the head, I will now proclaim that we're actually happy with it since it's been one of the things on the boat that has always been reliable.

 

[Nick F]

Many thanks Shawn - can you enlarge om the improved venting for me?
Nick

 

[timb]

we have a 30 gallon tank and worry about it after a few days with 4 people onboard .

 

[HeadMistress]

The 10 gallon tank worked fine, however we found that we averaged 6 gallons a day with a manual pump flush. This meant, when out we had to get daily pumpouts to be safe. That is very cumbersome.

Comparing the number of flushes a manual or electric toilet puts into a 10 gal. tank vs the number of flushes this Dometic 9.5 gal tank can hold is comparing apples and kumquats. Stop thinking in terms of gallons and start comparing the number of flushes.
When you get right down to it, this Dometic unit is actually just a HIGHLY glorified portapotty...and if a 5 gal portapotty can easily hold up to 50 flushes, this version with a 9.5 gal tank should be able to hold at least 75 flushes even if you're not as frugal with flush water as you could be.

The average adult uses the toilet 5x/24 hrs, so it would take one person 15 days to use 75 flushes, 2 people at least a week.

The average flush from any manual or electric toilet is .6 gallons, .5 gal (2 quarts) of which is flush water. The average adult will contribute 3 gals/day to a holding tank. If two people filled up a 10 gal tank in a day, you used a lot more than .5 gal of water/flush.


But using this Dometic unit, there'd be no need to use more than a pint--just what runs down the bowl from the channel in the rim--for a urine only flush...that much plus about a quart added to bowl ahead of solids. Do the math and you'll see that you'd need at least a 30 gal, maybe even a 35 gal tank to hold as many flushes from a manual or electric toilet as this 9.5 gal can hold.

Nick, I can find all kinds of info as to how far a macerator pump can be from a tank from which is it's PULLING waste...but nothing about how many feet a macerator pump can PUSH what it pulls out. Where did you find that it can deliver to another tank further than 6' away?

--Peggie

 

[Nick F]

Quote:
Nick, I can find all kinds of info as to how far a macerator pump can be from a tank from which is it's PULLING waste...but nothing about how many feet a macerator pump can PUSH what it pulls out. Where did you find that it can deliver to another tank further than 6' away?
--Peggie

Peggie - I am assuming this from gut feel, since the waste will be macerated. I think I will be able to use 1" hose downstream of the macerator and I would put fresh water behind the pumpout to clean the hose.

Nick

 

[Ddog]

I installed this toilet in our 26 Tollycraft last year and am very happy with it. A vast improvement over the original recirculating toilet!
One minor annoyance: after I carefully installed the tank square to the wall of the head I discovered that the toilet bowl did not sit squarely on the tank, it is turned a bit towards one side of the tank, so do a “dry fit” to check this beforehand.

 

[FF]

These are basically RV toilets , so first one should check the toilet location and see if a larger sized holding tank could be fitted under the toilet location.

This should be the standard location for most boats , but,,,,

A larger holding tank that can be fed by gravity might be large enough to only need to pump out every month .
To complete the finest cruising plumbing system the holding tank would use a bottom feed to the macerator pump and a high quality (Dupree) tank valve.

If a cheapo boat macerator wont push the waste out high enough , Obendorfor and other companies have far better pumps.

"Do it once, do it right , and never be bothered again."

IF only NA and boat assemblers realized folks would pay for less bother!

 

[HeadMistress]

after I carefully installed the tank square to the wall of the head I discovered that the toilet bowl did not sit squarely on the tank, it is turned a bit towards one side of the tank,

Apparently the holes in the tank for the studs were were slightly mis-aligned, 'cuz if you look at all the photos of this toilet, the bowl sits facing exactly straight forward. If you'd caught it in time, you could have returned it for a replacement.



--Peggie

 

[Nick F]

after I carefully installed the tank square to the wall of the head I discovered that the toilet bowl did not sit squarely on the tank, it is turned a bit towards one side of the tank,

FF and Peggie - I am looking at the installation manual and it is evident that the misalignment could occur in either of 2 places - at the tank top (4 bolts) OR between the black plastic transition piece (which contains the trapdoor valve) and the bowl. From the pictures in the manual I cannot see what holds this upper connection together, but I can see a shiny metal band. If this is like a hose clamp, maybe it can be loosened and the bowl rotated.

If, in fact, the misalignment is at this upper connection, the foot pedal (which mounts on the plastic transition piece) should still be "square" to the tank - it might be interesting to check this.

I love working on other people's problems!
Nick