If your IP31 is as old as mine one thing lead to another. My
head thu
hull was completely frozen and I could not understand why the two hoses, pump waste all that way to return to the tank?, how many gallons of stuff just set there. I had to replace my holding tank and the
thru hull. I replaced the tank with a ronca and the thru hull with a new thru hull, flange adapter and a
single marine ball valve and eliminated that double one. I also installed a new head with a house hold bowl same brand as original but the larger seat. Fit just fine. I then replaced all the 1 1/2 sanitary hoses with new. Most of my sailing is coastal and did not want to accidentally leave it to pump overboard, so this is the way I put this together. I piped everything to the top of the holding tank, I did not want a pipe to break off from the holding tank and spill an entire tank again. I ran the discharge of the head under the sink then turned it back to the top of the holding tank under the V-berth. then installed a dip tube in the tip of the holding tank as a discharge. This line goes back to under the sink where I installed a Y valve and connected this to the
deck pump out and a single line along under the starboard settee to the thru hull next to the nav station. Just prior to the discharge I mounted a whale manual sanitary pump.
The way the whole thing works is everything goes from the head to the holding tank so no accidental discharges. From there thru the Y-valve to the deck pump out. If I am off shore I turn the Y-valve towards this the thru hull, open the the valve then manually pump the whale pump to empty the holding tank, takes less than a minuet. I did install a electronic tank level with the panel above the head under the port hole so it can be checked with every use. It's only 14 gallions and fill quickley when the grand
kids are on the
boat It works very well for me. No accidents, no clogs and no problems. If you need more info PM me.