Toilet to waste tank Hose Path

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Our toilet discharge hose routes straight from manual toilet under floor under chart table and up to tank. The toilet overflows as I believe there's not enough water height above Joker valve to back pressure it closed. Is there a recommended best route for my 89 C34?   I plan to rerun sanitation hose with a loop located in the storage compartment behind the chart table with a max height about 10" above the top of the waste tank. Straight run up to loop from the tank, with exposed hose along hull surface under  the chart table. This will result in only one uphill run of hose, from toilet outlet to top of the loop.   I may add a vacuumn break to loop, but rather not.

Any help appreciated.

Craig Illman

That should help, but the joker valve itself should be adequate. Have you replaced it?



Yes, and I plan to reinstall another new one from Jabsco today. Jabsco instruction asks for 8" of hose height above toilet outlet.

There is not much pressure on the valve exerted by the existing installation.  I wonder if one of the newer toilets may be less in need of back pressure at the outlet.  Tank venting is good.


OK, I'm not on  my boat right now so I can't say for sure, but...
doesn't the hose come out of the head and go into the holding tank at the top of the tank, meaning there should be at least a 10" rise from the head?


When does the toilet overflow? I find it hard to fathom how a toilet that overflows has not been corrected in over 25 years. Is this happening every time the toilet is used?
Tom Mallery, C34 #1697, 2004 MKII, Splash Dance


Having just serviced the head on Eximius, I found that our head overflows if the control valve  on top of the pump housing is left in the Flush (left hand/open/ aft) position.

We now instruct all users to leave the control in the right hand/foward/dry position.

If it's yellow let it mellow, if it's brown wash it down.



Paul & Peggy
1987 C34 Tall Rig Fin Keel - Hull # 463

See you out on the water



I replaced my tank and hoses this past winter.  Never had any issues before or since.  Hose runs through the head under the nav table floor into the tank compartment.  Ties into the tank at the top corner.  I would say it's just about 8-10" above discharge at the head.  With all the C-34's out there with the same configuration, I tend to think it's a problem with the head itself.  I have a Raritan PH II head though.

Mike and Joanne Stimmler

Your head is not overflowing from the holding tank, it's sea water from the supply line because the head is below the water line and that's why you need to put the flush valve in the dry bowl position when your done with business. Many people (and sailors too)also close the thru hull valve because the flush valve is not 100% reliable. I've never had a problem with the holding tank hose routing and it's the same as yours. I did however wake up is the middle of the night to the sound of water dripping and the whole head floor  was full of water. One of my visitors had used the head and had not pot the valve in the dry bowl position. Thank God for the shower drain pump, it saved the day.

Mike and Joanne Stimmler
Former owner of Calerpitter
'89 Tall Rig Fin keel #940
San Diego/Mission Bay


Mike and Paul are thinking along the same line as I am. I cannot imagine the holding tank draining back to the head. We never had a problem with the supply line backing up when on dry. When sailing and heeling, if someone did not put the valve in dry, we could get water from the supply side. Rarely happened.
Tom Mallery, C34 #1697, 2004 MKII, Splash Dance


It should be pretty obvious if it is "black water" as opposed "fresh seawater".
1990 hull #1014, San Diego, CA,  Fin Keel,
Standard Rig


Thanks very much for sharing.

I am sure the toilet's overflowing from the waste tank, as the intake line was shut off. Also the problem occurred with the valve in the "Dry" position. Our intake is only fresh water from the Stbd tank. I believe my problem occurred due to the waste tank being full, and as the boat rocks, the water sloshing in the waste tank resulted in pulsating pressure on the joker valve. Perhaps the new J valve with be less sensitive.  If we overflow again, I plan to install the newer Jabsco toilet with the Twist'n'Lock handle, which is suppose to prevent flow back, or possibly an electric toilet.

Part of the problem was that , though we had just gone through a pump out, the tank was still filled. It turns out even with our vent line removed to prove we had a vented tank, the pump out station could not suck out much from the tank. So we'll try another station net time.

Any suggestions on how to determine that the W. Tank is near full?  I don't find tapping on the tank to be accurate. For now we plan on being diligent about pumping out.

Thanks again for your thoughts.


Sounds like you perhaps have a clogged hose problem somewhere. Also, I find it odd that you flush with potable water from Starboad water tank (if I understand you correctly) kind of a waste of valuable drinking water. I replaced all my hoses last year, but still have a Jabsco toilet and the standard factory hose set up with a macerator on y-valve and stanchion vent. All works well. Never had a problem pumping out at pump station. Goes fast, then flush with their hose, then pump out again until their hose runs clear. Good luck.
1990 hull #1014, San Diego, CA,  Fin Keel,
Standard Rig


About knowing the level in your holding tank, the best gauge to get is advertised right on our site:,2682.0.html

I know this is an old link, I'm sure Dennis is still in business (surprised if he's not).  I have the precursor to his product, when he was with the Accugage company.  I have an Accugage sensor that monitors both water tanks and the holding tank.  Simple to install and easy to use.  Great to see when the water tanks are close to empty, and when the holding tank is full.   I understand when Dennis spun off with his own product, he improved the design.  So his product is better (by the way, Accugage is out of business....)
Roc - "Sea Life" 2000 MKII #1477.  Annapolis, MD


I just installed a Scad Tech tank monitor on my holding tank.  Same one that Roc listed above, although the company name may be different now.  Dennis is still involved although I'm not sure in what capacity.

Two pieces of foil tape you put on the side of the tank and a couple of wires to a display gauge. 

You will probably have to cut out the side piece of wood holding the tank in place to get the foil tape on but you can easily glass it back in place.  That's the hardest part other than finding a place to put the sensor.

Stu Jackson

Quote from: Mike and Joanne Stimmler on June 24, 2015, 01:47:17 PM
Your head is not overflowing from the holding tank, it's sea water from the supply line because the head is below the water line and that's why you need to put the flush valve in the dry bowl position when your done with business. ....................

In addition to what Mike said, the small short white hose that is supplied with toilets should be removed and replaced with a vented loop.  Some have put them in the head, others in the nav station storage locker (where mine is).

This hose/vented loop is between the pump and the head ring where the water comes in when you flush (NOT the inlet hose from the seacock!!!).   For MANUAL toilets.

This prevents backflow and it doesn't matter what position your lever is in once installed, although I always leave my PHII on dry.

It's actually part of every single toilet installation manuals.

I know of one C34 skipper who's never bothered to do so.  :D  He's still afloat!   :clap

My outlet hose to the tank does not have a vented loop or any loop other than the rise going into the tank.

Peggie Hall has always been telling us that heads can pump for 6 feet, so I just pump on dry for a bit.  Never any issues.
Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

"There is no problem so great that it can't be solved."