Adding Discharge Pump

[Seawindii]

I am in the process of replacing all my sanitation hoses and Y valve and want to add a discharge pump while I am at it. While reading the installation manual for the Sealand Sanipump it says I need to add a second vented loop on the output of the pump. Not sure if this is true as I am also adding a Y valve between the pump and the holding tank.

Just wondering if some of you might be able to give this a sanity check. Is there a better way?

[Cheechako]

Hmmm... so it says to add a loop between the output of the macerator/discharge pump and the seacock? I wouldn't. I'd make that as straight and free flowing as possible. Assuming you usually have the seacock closed unless pumping.

[Seawindii]

That was my thought. But you can certainly see if the seacock was open and the Y between the holding tank and pump wasn't set correctly it could cause backflow into the holding tank. I'd prefer it to be more idiot proof but maybe this is how it's done.

[hellosailor]

In the interests of KISS, you could (should?) eliminate the two Y valves closest to the head, and the hose between them. That would mean the head always pumps into the tank, yes, and then any "direct" discharge still has to be FROM the tank, but isn't that a small price to pay for eliminating the extra fittings and hose?

Putting in the second vented loop will act as a siphon break, cheap insurance against the chance of the discharge line siphoning back and filling the tank and the entire system. Ugh, what a mess that could be.

Just one man's opinion.

[Seawindii]

I knew there had to be a better way. Your suggestion makes sense. I was making it too complicated. The second vent loop and pump placement will be a challenge. Back to the drawing board. Thanks!

[Stu Jackson]

Do you only have one outlet from the holding tank?

[ranchhand]

"sanity check". Pun intended?

[Seawindii]

Stu... I have basically as in the diagram. One inlet, one outlet. Stainless custom tank almost inaccessible without major deconstruction.

[Seawindii]

So here is the latest config. I eliminated the direct discharge piece, which simplifies things considerably. Direct discharge will be accomplished through the tank/pump.

Question: As I have eliminated the Y valve to thru hull on the output of the head do I really need the vent loop between the head and the holding tank?

[hellosailor]

Suppose you moved the discharge Y valve, and the deck pumpout, to the left side of the vented loop. Which should already be right up under the deck. Less plumbing.

And of course move the discharge pump to the other side of that loop, down by the thru-hull.

From what I can tell the vented loop in between the head and the holding tank isn't necessary, but it ensures that if you have a leaky or defective joker valve, the holding tank can't empty back into the head. Practical insurance. If the run from the head to the holding tank is all downhill, not so much a concern.

[Capt.Don]

This is how I plumbed my SeaLand pump. Note, as per my similar post, my pump's duckbill valves somehow got inverted.

[Seawindii]

Don, looks like a similar set up. I am no expert but the output of your pump may need to go through a vented loop. If the discharge seacock is inadvertently left open, backflow could occur, which might overcome the ability of the pump valves to stop it.

Hellosailer, my drawing reflects actual routing of hoses currently. Unfortunately I don't have much room to play around with.

[Capt.Don]

Seawindii, not quite - I have separate thruhull discharge thruhulls for head and macerator and a y-valve to route head discharge to the holding tank or overboard. The way you have this setup, you can only flush the head to the holding tank. Your y-valve only controls whether the macerator pump or shore pump-out is used to empty the holding tank. Is that what you want? I find it convenient to dump directly overboard (outside 3 mile limit) and bypass the holding tank completely.

[hellosailor]

Seawind, I'd say it was that "American Puritan heritage" thing, but sailboats world over seem to be afflicted with the same lack of attention to proper head plumbing. Or installation. Or just leaving space to correct either.

Or, maybe that's intentional, to ensure the gentler side stay ashore?

[Terra Nova]

Originally Posted by Seawindii

So here is the latest config...

Eliminate both vented loops. Plumb head discharge as directly as possible into the top of the holding tank, with no sharp turns. Replace the Y-valve with a sanitary-T. And plumb the waste discharge pump directly from that T, overboard. Keep the seacock closed unless pumping overboard.

Keep it simple. Take care to run hoses so they are as short as possible, that they pitch down to their destination (go high at the head, to pitch down to tank), and that there are no traps.