Back in March Peggy answered a series of questions I had regarding fittings on a new holding tank we are getting. Ronco will make the tank and D&D is making the mold for them. A number of things including Dave, the mold maker, having back surgery have delayed the tank delivery. After again rereading your book and your March 2005 responses in the Head Mistress Forum, I’m still puzzling about the fittings. I understand the vent, its importance and the need for it to be inboard to accommodate heel. Also we can keep the vent hose relatively flat, probably 35º off the horizontal, and certainly under 45º. We will have Ronco add an internal suction tube for the discharge. I read your recommendation to put the discharge fitting on the top of the tank. I can do that with a lot of effort in routing the 1½” hose. The existing discharge hose would install much more easily if I had a fitting on a vertical tank wall. It would result in 5 or 6 gallons of the 20 gallon tank being above the discharge fitting. The hose from the discharge runs to an existing Y-valve. I’ll keep that valve rather than install a second, off-shore discharge fitting. I found 90º elbows from Marine Products International under sealandservices.com and am considering using them to route the hose from the head to the tank. Elbows would let me more easily route the discharge hose from the top of the tank to the existing Y-valve. Would I be better off with elbows or a wall mounted fitting? What problems will I have if I install the discharge on the vertical wall rather than the top of the tank? I have only 5-3/4" forward of the tank to route the 1½” inlet hose. I’d be able to keep the hose shorter and the vertical rise lower if I used two elbows, including a 90º elbow at the inlet fitting on top of the tank. I think that is better than a loop of hose above a vertical nipple on the top of the tank. Is it? The one part of your earlier recommendation I do not understand is the need for the inlet fitting to be inboard. The discharge of the head is close to the athwartships centerline of the tank and about 20” below the top of the tank. The head and tank are on the port side of the boat. When the boat heels on a starboard tack, the contents of the tank will run to its outboard side and back up to the inlet if it is outboard. By the same token, on a port tack the contents will back up to the inlet if it is inboard. The head outlet, being pretty much on the tank centerline would be the same height below either the inboard or outboard fitting when the fitting is “downhill.” I know the outboard fitting will get closer to the waterline, but the waterline is outside of the boat and as long as I have the head inlet valve closed the sea water better stay outside. My bottom line from the preceding paragraph is I can’t figure out the preference for an inboard inlet fitting. I’d locate the fitting on top of the tank near its centerline to minimize the length of run from the head. And in anticipation of Peggy's question … we installed a Lectra/SAN in our other head a few fears ago and love it. The tank replacement is to get us into no discharge zones.
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I think you're over complicating it...
In an effort to avoid buying any more hose, even a few short pieces. "The existing discharge hose would install much more easily if I had a fitting on a vertical tank wall. It would result in 5 or 6 gallons of the 20 gallon tank being above the discharge fitting." I'm trying to visualize what you mean by that. If I understand you correctly, you want to put it more or less in the middle of the tank wall. If there would be a pick-up tube to the bottom, it SHOULD be ok...but without one, no way. If the pickup tube should ever drop off the fitting (which I've seen happen) you won't be able to pump out more than is above the fitting. IMO it would make more sense to just buy a piece of hose that's long enough to get to the top of the tank from the last inline radius fitting...or if there are none, from the toilet. A few feet of AVS96 for $5.50/foot won't bankrupt you! You can use an elbow for the vent fitting on the tank. Why should the inlet from the toilet also be inboard? The waterline has nothing to do with it...it's all about gravity--liquids flow downhill. So you want the inlet fitting inboard for the same the reason the vent should be: Putting the vent fitting inboard prevents waste from spilling out the vent when you're heeled...putting the inlet fitting inboard also prevents waste from running back toward the toilet and filling the bowl (the joker valve in toilet will only slow it down, it won't keep it out of the bowl). When the inlet is outboard, you'd need a loop in the head discharge line--not necessarily vented, but high enough to keep waste from getting over the top of it. I would have the second discharge port installed in the tank, even if you don't plan to use it any time soon. Better to have it, with a threaded plug in it, and not need it than wish later that you'd had it installed when they made the tank.
In an effort to avoid buying any more hose, even a few short pieces. "The existing discharge hose would install much more easily if I had a fitting on a vertical tank wall. It would result in 5 or 6 gallons of the 20 gallon tank being above the discharge fitting." I'm trying to visualize what you mean by that. If I understand you correctly, you want to put it more or less in the middle of the tank wall. If there would be a pick-up tube to the bottom, it SHOULD be ok...but without one, no way. If the pickup tube should ever drop off the fitting (which I've seen happen) you won't be able to pump out more than is above the fitting. IMO it would make more sense to just buy a piece of hose that's long enough to get to the top of the tank from the last inline radius fitting...or if there are none, from the toilet. A few feet of AVS96 for $5.50/foot won't bankrupt you! You can use an elbow for the vent fitting on the tank. Why should the inlet from the toilet also be inboard? The waterline has nothing to do with it...it's all about gravity--liquids flow downhill. So you want the inlet fitting inboard for the same the reason the vent should be: Putting the vent fitting inboard prevents waste from spilling out the vent when you're heeled...putting the inlet fitting inboard also prevents waste from running back toward the toilet and filling the bowl (the joker valve in toilet will only slow it down, it won't keep it out of the bowl). When the inlet is outboard, you'd need a loop in the head discharge line--not necessarily vented, but high enough to keep waste from getting over the top of it. I would have the second discharge port installed in the tank, even if you don't plan to use it any time soon. Better to have it, with a threaded plug in it, and not need it than wish later that you'd had it installed when they made the tank.
I made it too complicated
Yes Peggy, I did over complicate it. With your thorough, patient explanations I now know what fittings to specify. You provide a wealth of information to us boaters. Thank you!
Yes Peggy, I did over complicate it. With your thorough, patient explanations I now know what fittings to specify. You provide a wealth of information to us boaters. Thank you!
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