PVC pipe and holding tank pumpout

[Chris & Lenore]

Our holding tank and position does not allow space for a top mounted "dip tube". I have read that the problem with a bottom mounted pumpout location is sewage sitting in the hose.

Could I not simply use a 90 degree elbow to PVC pipe and run the pipe vertically - transitioning to hose when it's above the top of the holding tank? The pumpout hose has to run back along the top edge of the tank anyway, so if I size things correctly and use a second 90 degree elbow, the whole assembly could be held securely by the holding tank mounting straps.

Are there any "downfalls" to using PVS pipe if properly supported so it can't move independantly of the tank?

The other alternative is to use $15/ft hose but that gets expensive.

Thanks,

Chris

 

[alexco38]

Been using ABS for over 8 years. PVC isn't good enough. See picture.

A short Trident hose for flexing, ABS up to the top and Trident hose for the pump out.

 

[Don S/V ILLusion]

The 90 deg elbows will get you every time in that application. I'd suggest you do anything BUT create a routing which requires multiple sharp turns.

 

[Chris & Lenore]

Excellent replies! My goal with the ABS is to not use flex hose where sewage will stand in it.

I hate putting in the 90 degree elbows but can't see a way around at least one in the pump out. I assume there are large radius "sweep elbows" that would be more free flowing than the standard 90's.

I'm anxious to get the tank this weekend so I can see what placement options I have. It should fit fore/aft as well as crosswise in the v berth area. One way should maximize the v berth storage, although there really isn't that much.

Thanks again for the replies. On, and I do plan on 1 inch for the vent hose - that was suggested several times.

Chris

 

[Peggie Hall HeadMistress]

I hate putting in the 90 degree elbows but can't see a way around at least one in the pump out. I assume there are large radius "sweep elbows" that would be more free flowing than the standard 90's.

There are, and you can find 'em in the plumbing section of any of the "big box" hardware store. Connect the radius to a threaded tank fitting...ABS pipe to the top of the tank...hose to the deck pumpout fitting.

I'm anxious to get the tank this weekend so I can see what placement options I have. It should fit fore/aft as well as crosswise in the v berth area.

You're buying a tank that has no fittings installed? Do not buy a "Fittings relocation kit"...they're overpriced and include parts you don't need, plus you have to have access to the inside of the tank use one. And if you're buying an off-the-shelf tank from a marine store, I strongly recommend that you check the wall thickness...most of 'em are pretty thin--SO thin that ALL vertical walls have to be supported to prevent bulging.

I know you're eager to get a tank installed, but it's always cheaper and easier to do it right the first time than it is to do it over...so I think you'd be smart to slow down and consider more options...starting with the Ronco Plastics tank catalog. They make TOP quality thick walled water and waste tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular. And they install fittings in the sizes and locations specified by the customer when they make the tank. I highly recommend them! If you go with a tank from Ronco (no relation to the veg-o-matic Ronco, btw), you'll lose a whole two weeks...a very small price to pay to get it right the first time. I'll be glad to work with you to spec out your plumbing if you want to contact me via email.

I'm recovering from eye (glaucoma) surgery and have to be inactive for at least a week, so I have time to drop in here and try to help a bit.

 

[Chris & Lenore]

Thank you for the excellent advice - makes perfect sense.
I forgot to ask about capacity. I was thinking originally of shoehorning in a 39 gal tank. I have had several people say they would go 25 - for easier installation , less "full weight" to support and less use of storage space. It's usually just the two of us with a third about half the time. We sail the Great Lakes do there are no issues getting pump outs. A week max would work for us. Does a 25 gal make more sense (original was 30 gal?

Thanks,

Chris

 

[dlochner]

Thank you for the excellent advice - makes perfect sense.
I forgot to ask about capacity. I was thinking originally of shoehorning in a 39 gal tank. I have had several people say they would go 25 - for easier installation , less "full weight" to support and less use of storage space. It's usually just the two of us with a third about half the time. We sail the Great Lakes do there are no issues getting pump outs. A week max would work for us. Does a 25 gal make more sense (original was 30 gal?

Thanks,

Chris

If a smaller tank gives you room to use a dip tube I would go with the smaller tank. We have a 20 gallon tank that will go about 5 days between pump outs. Also consider how you will run the inlet, the shorter the inlet the less water you have to pump to clear the hose.

 

[John Nantz]

Hey Peggie! Glad to see you stopped by! I hope the surgery thing went okay. That's not a place where one wants to have a problem. Seems scary to me.

I have a question: What is a good strap material and end connectors to use for a tank hold down?

The existing setup has the straps going under notched oak or mahogany hold down wood strips and then around the tank. The OEM plastic straps are kinda typical of what is used for shipping things and have the ends overlapped with some kind of a crimp gizmo which I can't reproduce.

I've been thinking about up-sizing the holding tank and this is one of the little details to address. The current tank is rectangle on three sizes but sloped on the fourth, near the side of the hull.

I'm also thinking about upsizing the fuel tank, too, but getting the lazarette organized for everything is requiring some deep thought.

 

[Peggie Hall HeadMistress]

I forgot to ask about capacity.

And I forgot to give you the link to the Ronco Plastics catalog: Ronco Plastics Marine Catalog

I was thinking originally of shoehorning in a 39 gal tank. I have had several people say they would go 25...We sail the Great Lakes do there are no issues getting pump outs. A week max would work for us. Does a 25 gal make more sense (original was 30 gal?

I'd go with 30...39 is overkill IMO, 25 is marginal...Pumpouts may be easy to get, but having to up anchor--or worse yet, have to come out of the middle of a raftup--in the middle of long weekend to go get one is a major PITA...so you want to have a little room for an extra crew or another day. Here's the math...these are AVERAGES: the average adult uses the toilet 5x/24 hrs. Avg flush volume from a marine toilet: .6 gal (2 litres)...that's 3 gal/day for each person continuously aboard. So a 30 gallon tank should last two people 5 days...on average. Too much beer, too much flush water can reduce that to 3...Some careful flush water conservation and judicious use of the lee rail will extend that to a week.

As for your question, John...
What is a good strap material and end connectors to use for a tank hold down?

Tanks rarely bounce up and down much...they really only need to be secured from sliding around. But if you think it has to be strapped down, lawn chair webbing is great strap material. Fold down the ends for added strength and secure to the hull with a pop rivet tool (cheap at any hardware store).

If, otoh, you decide that securing the tank from sliding is all that's needed, some quarter round or picture frame moulding at the corners held down with Gorilla glue or other heavy duty adhesive of choice.

 

[Winkfish]

How are you enjoying kretirement, Peggy? Maybe a new thread to update us on your doings?

 

[John Nantz]

Peggie - Thanks for the tank strap details. Never thought about lawn chair webbing - it's pretty strong and really doesn't stretch hardly at all.

I was just on the boat today trying to figure out some changes to the dodger when it went from a light mist (missed Oregon, hit Washington) to a rain so I called it quits and planned to go back tomorrow. Just checked the weather forecast and .... rain. Well, Maybe on Tuesday.

Speaking of retirement, there's a popular saying: "I don't know how I ever found time to go to work."

 

[Chris & Lenore]

Hi Peggie,

Thanks again for the info and I hope your recovery is coming along well.

I took your advice and went with a 30 gal tank. There was a Moeller tank that's a perfect fit, so I decided to go with that over the Ronco. It's a thick wall version (15 mm) and seems comparable.

I'll post a few pics as the project progresses.

I am also upgrading the head to "twist N lock" by replacing the pump assembly. It turns out an entire new pump is (at the store I was at) roughly the same price as a gasket/seal kit.

Chris