Holding Tank Choices

[Bowdrie]

Perhaps this should have been a poll.
Anyway, I'm in the middle of a re-fit and one of the jobs is replacement and repositioning of the holding tank.
The new tank is roughly rectangular in shape and mounts on edge under the side deck directly under the deck fitting.
As such it's a straight shot down the dip tube with no bends to contend with.
I have a choice to make regarding the manual pump-out scheme.
I can either use a "sanitary tee", with the run of the tee to the deck and the branch of the tee to the Henderson or use the dip tube for deck suck-out only and use a bottom outlet to the manual pump.
With a sanitary tee it's an easy job to disconnect the hoses, cap the fittings and the tank can be removed without any chance of "unfortunate happenings".
With a bottom outlet the plumbing is much simpler, and the runs are shorter.
However, should service/removal be required things get more complex.
The Henderson has easy access, and a bucket can easily be placed so that upon removal of the cover/cap the contents of the hose can be contained.
I'd be interested in hearing what you guys think of top outlet vs bottom outlet.
I'm sure that horror stories abound no matter the choice.

[rslifkin]

I'd use the tee. My boat was built with a dip tube pumpout with a tee for the macerator and deck fitting. It worked fine for 33 years until I replaced the tank, so I kept the same configuration for the new tank. I like only having connections on the top of the tank and no hoses that are always full of sewage (should reduce the risk of hose permeation).

[peghall]

I suggest you add another discharge fitting with "dip tube" to the top of the tank, giving you a dedicated pumpout line and a separate dedicated overboard discharge line and eliminating tees, y-valves etc altogether. You'd prob'ly have to remove the tank to do it, but it's actually a pretty easy job using a Uniseal and Dometic's over-priced but simple to install "diptube kit." Or, I can walk you through how to make your own for a fraction of their price. Send me a PM if you'd like to do that.

--Peggie

[Bowdrie]

Originally Posted by rslifkin

I'd use the tee.

That was the plan, I've got the tee ready to mount.
But you know how it is, you see other possibilities and start to second-guess yourself.
The original tank was bottom outlet and, (thankfully,) never had any leaks/problems, (maybe I was just lucky).
Your point about permeation is valid, this time the hose is more "high-tech", at least it costs more.

[Bowdrie]

Originally Posted by peghall

I suggest you add another discharge fitting with "dip tube" to the top of the tank, giving you a dedicated pumpout line and a separate dedicated overboard discharge line --Peggie

I understand the reasoning behind that, it eliminates the tendency of the dockside suction to try and suck backwards thru the manual pump-out hose, and using a dedicated manual pump-out hose eliminates any air leakage from the deck plate to ruin the suction.
In my case the only way to use two dip-tubes would be to move the inlet fitting from the top of the tank to the forward side of the tank up as close to the top as I could get it.
There simply isn't enough room on the top of the tank to allow 3 separate fittings and corresponding hoses with the routing necessary to achieve that.