Black water discharge from manual vs electric head

[Dan_Y]

My question is whether or not an electric toilet can pump as well as a manual head to sufficiently empty the lines to the holding tank.

Our new-to-us '08 H36 has a Jabsco pressurized freshwater electric toilet model 37045-7000 and I wonder if it can expel black water as well as the manual Jabsco head we had in our '91 H30? My concern is based on what I learned from Peggy's excellent book, which was that I needed to pump the old head about 10-12 strokes to empty the bowl and move the water through about 8-10 Ft of 1.5" sanitation line to the holding tank. The lines appear to be 12-16ft in the H36.

The electric head apparently relies on the centrifugal impeller within the macerator to pump macerated bowl content directly through the joker valve and into the lines (see p. 62 & 69 of the book). But once the bowl is empty, I did not think a dry centrifugal impelled pushed enough air to empty the lines into the tank. Do electric toilets rely on gravity to drain the lines after emptying the bowl into the lines?

After just rebuilding the macerator, it looks like it could run "dry" for several seconds after emptying the bowl with out damage, unless the motor shaft seal relies on water for lube and may shorten its service life. The chopper blade and impeller are a close fit to the macerator housing but don't touch anything but black water. Note, the impeller is a hard disk with vanes and is not like the rubber impeller used in engine raw water pumps. It looks more like a swimming pool pump impeller.

I would run the macerator for maybe 5 sec after the bowl emptied if I thought it was still pushing the water down the line to the tank, but am not sure about damaging the macerator. Does anyone know if that would help with this model of toilet?

My proposed solution once the new lines are in is to essentially follow Peggy's advice and end the day with a couple of manual "full bowl" flushes to keep "clean" residual water in the line. I'll just have to visit the pump out stations more... but the boat will smell better!

Thanks for any thoughts.
Dan

 

[Peggie Hall HeadMistress]

The short answer to your question is, no. 6' is about as far as that toilet will move bowl contents in any reasonable flush time...your tank is twice that distance from the toilet.

Your toilet should be equipped with dual flush rocker switches--one that lets you bring in water ahead of use, then allows a "dry bowl" flush...the other switch simultaneously brings in water and discharges bowl contents. If you don't want to "fry" the discharge impeller, you have two choices...use only the simultaneous flush switch long enough to get bowl contents to the tank (which will fill up your tank with flush water)...or "dry" flush for 5-7 seconds each time, then at the end of the day flush enough clean water through to clean out the discharge line.

Alternatively...If you can put a loop--doesn't have to be a vented loop, just a loop--in the discharge line that's higher than the top of the tank, you'd only have to flush long enough to push the bowl contents over the top of the loop...gravity would take it the rest of the way. The only other alternative would be to move/replace the tank to a location that's no more than 6' from the toilet. Since you're already replacing hoses, that might not be a bad idea...we might even find space for a larger tank.

 

[Dan_Y]

Thanks Peggy. The loop is an interesting idea and potentially the most workable alternative. Easy to do because it's 1-in discharge line at the toilet and I'll be using Trident 102 rubber sanitation hose that seems to be fairly flexible. But the 90 deg discharge port at the macerator slows the discharge down as well I would guess. The photo shows the bowl withe the macerator mounted on the left side. At least the 90 elbow can be rotated in any direction. Jabsco also makes another discharge port that has about a 20 deg bend, but can't be rotated and would flow straight back in the photo. That might be okay to get less restriction and more velocity thru the joker valve if I put the new loop in the line. The loop would also prevent backflow into the bowl I think.

The head is on the port side and the custom-fit tank is in the starboard transom locker (see figure). Not sure why Hunter chose to place the tank farther away...some sort of construction trade off that I don't understand.
Thanks Again for the info and ideas!
Dan

 

[Jerry Clark H356 SV Persi]

The H356 and 36 line is 17 feet from the toilet. I have a Raritan Sea-Era and it brings in enough water to not go dry while flushing. We have over 900 days on the boat since installing the Sea Era and I flush for 17 seconds at the end of each trip. This should clear the line. I also pour a small amount of Odorlos in the bowl. We have not had any problem with our line permeating.

 

[Dan_Y]

Thanks-Now I know how much to buy. I'm thinking about using sections of schedule 80 1.5" PVC in the straight run along the hull under the aft berth and along the transom under the lockers. The crawlspace under my house has PVC sewer lines running all over and there is no smell after 20 years. Would be less hose to replace in the future, but I also think the sch 80 to barbed fitting might not be the smoothest transition and cause water to pool at the transition. I have to look a bit closer.
Dan

 

[Jerry Clark H356 SV Persi]

I haven't measured it, so make sure you get enough. It could be a little more than 17 feet but that is a close estimate.

 

[Dan_Y]

The disappointing thing now is that a realize there is a low spot in the factory installation that keeps water in about 1/4-1/3.of the discharge line. I know this now from replacing the lines. There were several quarts of water in the old lines. I can't find a routing that will provide a downhill grade from the toilet or loop at the toilet to the tank. Boat drawings would be helpful, but impossible to get now that Hunter is gone. MH support for the Hunter builds seems to be thin.

 

[Peggie Hall HeadMistress]

Simple solution that might work (or may not...I haven't seen your installation): come out of the toilet immediately up and over a loop (not necessarily vented, just a loop) that's higher than the inlet fitting on the tank. That would give you a downhill run all the way from the top of the loop to the tank. It would also allow you to use a lot less flush water because you'd only have to flush long enough to push the bowl contents over the top of the loop, followed by enough flush water to rinse behind it. Gravity will do the rest. You would have residual flush water in the line between the toilet and the top of the loop, but it would be clean water....a little seepage back into the bowl wouldn't be the end of the world.