Holding tank pump-out hose size

[44kebeck]

I am re-plumbing my holding tank and have a question. If the tank is being fed by a macerator toilet, could I get away with 1" hose to a reducer at the deck pump-out fitting?

It would be easier (and cheaper) to route the smaller hose.

[sailvayu]

I would not do it myself. Many pump outs have a high suction and high volume to empty the tank fast. This has been know to collapse tanks with small or clogged vents. I am thinking a smaller hose would cause problems, possible collapsed hose. I always say It is best to save on labor but do not cut corners on materials. Surly it cannot be that much harder to run a 1-1/2" hose over a 1" ?

[Watercolor]

Yes, you can "get away with it". However, remember, on a boat Murphy is working overtime. And he doesn't sleep or get seasick. I agree with sailvayu.

[rsimon]

I read the post response with gratitude since I'm laying down my gray water waste
tank as well. But I have a similar/related question. On my gray water tank it has a
female fitting lower down allow for water suction/emptying as you know. Should I have a 90 degree elbow that turns up or a straight line that allows for draining easier? Thanks

[Watercolor]

If I understand your description. The grey water lines flow into a grey water tank from there to a thru-hull and overboard and maybe to a pumpout deck fitting.

I'm guessing that the output on the tank is at the bottom of one of the sides of the tank. You turn a valve and the grey water flows overboard (I'll leave the pumpout out of the discussion now.)

If that's the case, it's always best to have a straight run. Otherwise you have standing waste in the line.