Holding tank configuration options

[pdx_sailing]

I am installing a new Ronco 23gal tank. I will plumb the head directly to the top of the tank wo a Y valve. I will plumb a gravity discharge with a ball valve at the tank outlet to the through hull. I plan to use PVC or ABS pipe as much as possible with short hose connector to allow some flex in the system.

My question is can you have a flexible or curved / bent pick up tube to follow the profile of the tank next to the hull? This would give the shortest / straightest path to the deck pump out.

The other option is to "T" into the gravity outlet on the bottom of the tank and route up along the end of the tank, longer run with more bends.

What is the prefered Vent "hose" material? should / could this be PVC? Clear braided hose or sanitation discharge hose?

Is the first option an actual option, is one really better than the other?

Thanks

[Jammer]

I don't know much and am not an expert.

If I were going to try that I would install an inspection port in the top of the tank and utilize a clamp-type bulkhead fitting. The dip tube could then be made of rigid material, such as schedule 80 PVC that has been heated for bending, and held in place by the bulkhead fitting.

The inspection port will be necessary for the initial installation as part of the bulkhead fitting must be installed from inside the tank.

https://www.grainger.com/product/BAN...ting-316-1MKJ5

[Jammer]

For clarity, schedule 80 pvc can be threaded, and would not need a cemented threaded adapter fitting (which would be a weak point)

[peghall]

I'll be glad to help you sort out the best way to do this if you'd like to send me a PM.


--Peggie

[Bowdrie]

Originally Posted by pdx_sailing

My question is can you have a flexible or curved / bent pick up tube to follow the profile of the tank next to the hull? This would give the shortest / straightest path to the deck pump out.

The other option is to "T" into the gravity outlet on the bottom of the tank and route up along the end of the tank, longer run with more bends.

I've built custom tanks both ways.
With a nice thick fiberglass tank I had no qualms about using the heavy wall filament-wound T-fitting from Centek to glass into the bottom of the "bottom outlet" tank, it would never leak and would take a sledge hammer to break it.
And whatever may come, glass and epoxy could make things right.
With plastic tanks I want to think twice, or maybe thrice, about having a soft plastic threaded fitting at the bottom, not to say they can't work, many have just such an arrangement without any problems.
It's not a big deal at all to make an "angular" dip tube, but it should be able to be inserted/withdrawn from the tank without having to rotate, (duh).
This in general precludes threads.
There are ways around that by using some more special fittings.
Peg knows lots about this stuff.
Stuff like this can often be used,
https://www.environmentalmarine.com/...be-kit-310660/
And Marine Sanitation has all kinds of goodies for holding tanks.
https://marinesan.com/holding-tank-accessories-parts/

[AnsleyS]

PDX,

The most important thing that you need to know about installing a custom tank system is TALK TO PEGGY !!!

She had been in the business for a long time (sorry Peggy) and will listen to your ideas and give you good advice. Listen to her and follow her lead. She helped me do a two head system more than twenty years ago, and it has worked great since we put it together.

Think about two big vents, no bottom of tank outlets, and sloping piping.

Again, don't listen to me. Talk with Peggy.

[CaptTom]

But please, come back and post what you and Peggy decide. It'll be a good thing for all of us, and future viewers, to know.

Personally, I like the idea of the pump-out pipe running from the bottom of the tank, if it's structurally possible. Next best would be on a side, again at the very bottom, although in theory that leaves an inch or so of liquid behind, once the level gets below the top of the fitting. My least preference would be a dip tube pick-up.

That said, I've only done a couple of these in my lifetime. I'd love to hear what an expert would do.

[pdx_sailing]

I have taken Peggy up on her offer of assistant and I will post of the final design for future reference.