Hose size for holding tank...?

Ok, math lessons. I don't know pumps but do know math. First, 38 isn't 33% more than 25, it's 52%. Now as area. The area of a 25 mm circle is 491 mm and the area of a 38 mm circle is 1134 mm so it's 131% greater. So it's capable potentially of over 131% more volume. Now in practice it probably won't be that much but it's still a large number and shows how much the smaller hose could be restricting flow.

Now that doesn't mean it is restricting flow because the power of the pump comes into play. Perhaps the 1" is capable of handling all the macerator can pump. I doubt that though. If the manufacturer designed it with 1 1/2", they obviously felt that was appropriate.

I always use the "is it worth the risk to save those few bucks to not make it right" and toss in the scenario of a clogged waste hose or jacked up macerator. And maybe that's why the macerator needs replacing, because it was pulling and couldn't get the flow it needed.

Merry Christmas!

You want to use the standard 1.5" hose on the intake side as stuff will get clogged in 1" hose, especially with a reducer for stuff to hang up on. Discharge size for the pump you've shown is 1". The Sealand pump is far better but has a 1.5" discharge size also. I would recommend a brand other than the Jabsco one you've shown as they have had a lot of premature failures with that pump. I went through a string of them myself, but everyone else has been saying the same thing. Shurflo makes a direct replacement for that pump that is identical physically.

There are many ways to do a job the wrong way, and only 1 right way (usually). I will not do a job the wrong way and will tell a customer I'm doing it the right way or not at all.

I have very little experience working on pumps, but you caught my attention with 1.5" intake and 1" discharge. Couldn't that result in a clog in the pump, and be the reason it was changed?

No, the inlet is larger than the outlet size, because the pump has a chopper blade in it and the restriction allows the chopper blade to macerate the stuff.....and the restricted size allows the pump to build pressure to pump it overboard. Jabsco, sureflo, Johnson and another brand utilize this design.....

OTO, the Sealand brand utilizes a 1.5" inlet and outlet, but uses a diaprahm design.

Theory and math is fine but in the real world y really want the biggest possible hose when dealing with black water.

I hate those pumps... They usually can't run dry and I ve never seen one lasting more than a couple of years. Best holding tank pump is the sea land diaphragm pump which is twice the price but lasts 5 times longer.

Hey Norseman,
I'm like a bad check that keeps bouncing back. Heard that YF was trying to change the tone to get back to boats and away from arguments and confrontation. So figure I'd come back. As for sail into the sunset; I've still got a year or so left doing the Great Loop on Valhalla. After that, who knows. I've been trying to retire since I was 38, and can't seem to get the hang of it. Every time I try to retire I end up working harder and longer.
Thanks for the welcome back.

Counting on that, but it has to be earned (Be very good, and very bad).
In the late spring we'll be cruising around the Great Lakes & Georgian Bay for a few months, then head down the rivers for the Gulf in late August. I'll notify when we're moving on the thread Great Loop Cruise Video so y'all can watch off our bow cam or follow along on MarineTraffic.com (whenever they catch up to us). So subscribe to that thread.

Are you planning on doing the Mississippi the entire way, or shooting across the Ohio and doing the Tennessee, Tenn-Tomm, Tom Bigbee? I did the latter and it can be very slow going because of recreational boats having to wait at all of the locks for the commercial traffic. If I had done it a second time on the 75' Hatteras MY , I would've taken the Mississippi which would've been faster with the current and lack of locks, even considering the extra 300 miles. On the short 150 miles stretch from the Illinois canal to the Ohio.....we were doing 14 knots SOG, with our normal 10 knot cruise speed.

The Tennessee River is one of the nicest parts of the trip. On a delivery, the Mississippi is ok, but Kentucky Lake and Pickwick Lake are great. We're going to spend a long time in that area, keeping the boat there over winter. That is, when we get around to looping.

GalleyMaid eats everything. You could probably use them as a garage disposal.

Well, then I would mention how horrible it would be to not have a head you can use for 3 weeks! Finding a pumpout station in the Bahamas is like finding a Maine Lobster over there. How many feet of hose are we talking about on here on the intake side anyways? 1" hose is far too small to try to pull unmacerated sewage through......far too hard for toilet paper or one of those giant logs to get pulled through........But, all you can do is make the recommendation.

The flow rate isn't the recipe for disaster, the getting raw sewage items to pass through that size hose and getting hung up on the barbed fitting is going to be the recipe for disaster. I think it would be far better to put an expanded fitting at the tank and run 1.5" hose from the fitting on the tank to the pump. but either way is not right.