Dry pumping the head

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Duane Ising

On the Catalina 36 International Association website, there was a discussion regarding marine toilet plumbing. A gentleman there cited some material from you, Peggie Hall, which confused me. What I read seemed to imply that in the "dry" position, one could pump liquid waste all the way to the holding tank. I cannot see how that is possible in almost any installation I am familiar with. In my opinion, based on what I know about physics, pneumatics, and hydraulics, the only way to pump anything to the holding tank if there is any significant vertical rise in the discharge hose is to have a continuous "slug" of liquid throughout the hose. As I see it, if you are not bringing any more flush water in through the seacock, then I'm pretty sure you can only pump until you have moved the liquid past the pump, but not much further. To move a slug of liquid beyond the pump in the "dry" position would require that the pump compress air and move the liquid in the hose uphill, which I don't believe is possible. The heavy liquid will be pulled by gravity to the lowest point in the hose and the air will just bubble through it. I have experience designing pneumatic conveying systems which use air to move liquids and powdered solids, but there we are using very high flow rates and pressures, not the extremely low values we can generate with our hand pumps. Please explain if I have misinterpreted what was implied by the statements credited to you. Thanks in advance. Duane Ising Catalina 36 s/v Diva Di Punta Gorda, FL
 
Dec 2, 1997
8,958
- - LIttle Rock
Here we go again...sigh

One more time: I never said ALL the way to any tank, no matter how far from the toilet. However it's a proven fact that any marine toilet that's working anywhere near specs can move bowl contents up to 6 linear feet or 4 vertical feet in the dry mode. Further than that, it'll need a push from water. Which is why tanks should be within 6' of the toilet...and why, if the run to the tank is uphill from the toilet, it's a good idea to put a loop in the line close to the toilet that's slightly above the tank so that the toilet only has to push bowl contents over the top of it...gravity will do the rest. I didn't make this up...you cam ask toilet mfrs. I've also seen it for myself many times...as recently as last month in the Raritan booth at the Annapolis sailboat show. If you don't believe me, I suggest you see it for yourself. It's not hard to do...just stick a 6' piece of hose on the toilet discharge fitting, put some water in the bowl and pump in the dry mode. Cut 2' off the hose, aim the discharge fitting straight up...and do it again. If you don't want to do that, call the toilet mfrs.
 

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Peggie, the toilet is in the Vee berth and the

holding tank is in the lazerette will six strokes on the pump be enough. LOL ;D You get some of the most naive questions! I am not sure how you remain civil. Didn't anyone study plumbing 101? s--t runs down, don't chew your finger nails, and payday is Friday. Septic tanks are buried for more than aesthetic reasons. Gravity goes a long way to moving waste from the pot to the tank. Hang in there you still fill a need and are much appreciated. Thank you for being here when you are call upon. Edit to add: I am going to have to vent my holding tank above deck, the new filters that I buy are inadequate. I am thinking about 6 feet up the mast on the outside.
 
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Tom S

Duane, I think whats happening on the C36

Is gravity. We have the same basic set up (a '99 C36). Once the waste is pumped out of the head it almost a downhill run to the holding tank (at worst its a level run) . The good thing about the C36 Head to Holding tank set up is that it is well within what Peggie says is desirable "within 6' of the toilet and downhill". On our boats I think once you get the waste out of the bowl it will mostly flow down into the holding tank and with what Peggie says any "dry" pumping will only help move it along into the holding tank.
 

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Yes Peggie, I have great regard for you. You

provide a valuable service on this forum and I wouldn't try to take anything away from you on that count. I was quite serious about the need to vent my holding tank above deck. For reasons that I don't fully understand the filter cartridges that I had been using kept all odors from the cabin but the new ones don't do as good a job. I have disected the old cartridges and they contained charcoal and particle filters. I have not yet disected one of the newer cartridges but they don't trap the odors. For H2S they are rated for escape only. so I am not pleased with them. More to follow when I open one. Ross
 
Feb 26, 2004
23,067
Catalina 34 224 Maple Bay, BC, Canada
It's all my fault

I suggested that Duane post his qustion when the discussion on the C36 board got into this. Sorry for the need for the repeat on the answer.
 
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Duane

Thank you, Peggie.

Well, Peggie, it was interesting to read the specs you cited. I will bow to your experience and withdraw my question/challenge. To satisfy my curiosity, I may do as you suggested. Thanks for all you do for this forum.
 
Jan 1, 2006
7,619
Slickcraft 26 Sailfish
My Thanks too, to Peggy

You've just answered a question I had regarding the replacement of my head hoses. The current installation in H356 has the hoses running through the bilge to the tank which is a bit uphill. As per Peggy's post, I think I will make a loop within 6' of the toilet so that it will be a downhill run from there to the top of the tank. If anyone has done this in the 356 I would be interested in how you ran the hose. I am considering the loop in the lazerette. Any comments?
 
Dec 2, 1997
8,958
- - LIttle Rock
Ross, send me an email?

I'm in all the owner directories. We need to explore better options in more detail than is practical in a discussion forum.
 
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