Holding Tank Pumpout Physics

[Bob Bradley]

I'm presently replacing my vacuflush system with a Raritan toilet on my '86 45C. A PO converted the 140 gal original holding tank to a diesel storage tank. I love having the extra capacity for fuel, but they replaced it with a combination holding tank and vacuum chamber which only holds 10 to 11 gallons - clearly not enough. It is located in the fwd port corner of the ER, and plumbed in very professionally. I could probably fit a 30 - 40 gal tank there once I remove this one and rearrange a couple things. That would be much better, but still not really sufficient for longer trips.

Last season I removed the original live well from under the cockpit sole. I could put a much larger tank (75-100 gal) back there. I'm worried about locating it so far from the head, and also so far from the deck pumpout and the bellows style overboard pumpout, neither of which I want to relocate. What do you guys think about adding another 20 - 25 feet of 1-1/2" hose to the system to increase capacity? It would probably wind up being a foot or two lower in the boat than the current setup, however probably higher than the original tank below the galley floor.

 

[brettportzer]

On my 43 the holding tank is the forward keel tank, and it is fairly far from the aft stateroom and I called Raritan tech support and talked to them for a few minutes about it. Very accessible, I think I emailed them the question and he called me in the morning.
I believe they actually recommend using the 1” hose from the toilet to the tank, especially for longer runs.

 

[Pascal]

I converted my 53 MY to Raritan Atlantes’ a few years ago. The master head is at the back of the master about 10’ from the stern and the holding tank is under the floor at the bow. That’s about 35’. No issue.
You should probably had a pump out fitting close to the tank which will easier than running a hose to the existing pump out deck fitting anyway. A bellow pump should be fine for over board discharge. We use a VF bellow pump to assist the weak marina pump out sometimes, set up on the dock. It has no issues pulling waste from the tank and thru the 60-70’ pump out hose

 

[Bob Bradley]

Thanks for the replies. The plumbing is already in place from the old system. 2 y valves: flush diverter between tank and direct overboard and another for deck pump out vs overboard. Both overboard lines are properly vented. So all I need to do is replace 2 short hoses with 2 longer runs.