holding tank fittings..

groundhog · #1 (**permalink**) 06-25-2007

When you order these plastic holding tanks, what is the best type of fittngs to get?

I just talked to the fabricator and he says he can put on barbed or threaded, or whatever i want.

With polyethelyne, is there a strength issue when tightening the hose clamps?
Maybe order threaded and add a nylon or PVC hose fitting.

But maybe a threaded fitting allows just one more place for smell...

thanks,
roy

Sailormann · #2 (**permalink**) 06-25-2007

If you are talking about the fittings that your vent, intake and pump-out hoses attach to - then barbs are pretty well the standard. Warm your hoses up a little before you spend the requisite three and a half hours trying to get the little suckers to go on, and then double clamp them. If you use some type of lubricant - be VERY careful not to use something that is going to degrade your hoses.

The inspection port (can't imagine ever wanting to really use that for it's appellant purpose) is usually threaded, and screwed down really, really tightly with about 600 turns of teflon tape to make sure that stuff never gets out.

sailingdog · #3 (**permalink**) 06-25-2007

I would second using a hair dryer or something to warm the hoses... it does make them much easier to work with. For the input and output lines, you should use SeaLand Odor-Safe hose, which is pretty well recognized as the most odor impermeable and resistant hose on the market. Peggy Hall swears by the stuff IIRC. Vent hose isn't all that critical, unless you over fill the tank on a regular basis.

BTW, don't heat the hoses too much, since they can stretch and warp...and that is really bad.

Barbed fittings are far better on a boat, since you're likely to be using hoses rather than PVC pipe, which is more odor-resistant but subject to fatigue cracking, for the system.

Don't over tighten the clamps, as that can lead to stress cracks in the hose barb fittings...which is bad.

I recently installed an inspection/clean out port on my holding tank, and it is a clear plate, so I don't have to open it to do a visual inspection.

Lots of sealant on that port.

groundhog · #4 (**permalink**) 06-26-2007

Thanks for the info.

That is one of my concerns (see above). The strength of a barbed polyethylene fitting under hose and clamp compression.

I just realized that I may be forced into threaded input/output connections. My in/out will be on the bottom of the tank. The input will have a standpipe to the top of the tank. I will need to do quick right turns as soon as I exit the tank. Seems the best way to do that is with a threaded to barbed PVC adaptor (if I can find one).

I read a previous post of yours about the inspection port, so I have planned to install that.

My head compartment is just a bit forward and on the starboard side of the sailboat. My holding tank will be behind the head and above waterline. The head is half below waterline.

My waste port will be on the deck.

I am thinking my vent will be a 1 inch dia to the top edge of the hull side. Then I will put the vent on the top of the tank and as far inboard as possible. This will effectively eliminate any water getting into the tank when/if I heel and put the rails underwater.

The advantage of the side hull mount is that rainwater won't get into the vent. I am using just some type of thru hull for the vent. I will make the hose go uphill slightly inside the boat before going down to the top of the tank fitting. This will prevent rainwater from going into the vent.

groundhog

sailingdog · #5 (**permalink**) 06-26-2007

Groundhog-

IMHO, you'd be better off using a vent fitting for the vent hose. LINK

groundhog · #6 (**permalink**) 06-26-2007

Yes, I have one of those in my shopping bag, but I was going to return it.

I have read that the generally accepted diameter for the vent port is going up for some reason.

The one above is 5/8 dia I believe.

Hey, on your clear deck plate access. does that lid screw right into the polyethylene or do you glue the deck plate frame to the holding tank and then the plate screws into the frame?

gh

sailingdog · #7 (**permalink**) 06-26-2007

Groundhog-

The reason for the vent ports going up in size is to promote oxygen in the holding tank. The bacteria that cause the nasty odors are anaerobic, the ones that don't stink up the boat are aerobic, and need as much oxygen as possible.

5/8" is a decent size vent line, but it depends on how large the tank is.

My deck plate frame was 5200'd to the tank, and then through-bolted to the tank. The machine screws, washers and nuts were coated in sealant as well. However, my tank is a built-in fiberglass tank, so doing this wasn't as much of an issue as doing it with a molded polyethylene tank. Fiberglass isn't as "slippery" as the polyethylene is, so the sealant generally will hld it better. I also used a deck plate wrench I made to tighten the inspection port as much as possible... I don't want it to leak.

groundhog · #8 (**permalink**) 06-26-2007

Yeah, that's what I was wondering about. I thought you also had polyethylene. I read that just about nothing will stick to it.

I think I will just get a 4 inch threaded end cap put on as an emergency clean out.

gh

JustinC25 · #9 (**permalink**) 06-27-2007

I am almost finished with connecting up new hoses to my holding tank. I have one question though... How far do you really need to get the hose on the barb? Of course some are very tough and I actually sanded some of the barbs down a little to slide/force the hose on. Even then I could only get the hose maybe 1/3 to 1/2 way the length of the barb fitting. They don't seem to want to budge, but then again I don't want to have to deal with these again in the near future.

Also I noticed West Marine had two different types of nylon fittings for the tank. The white and then the black which cost 3-4x as much. I ended up buying the white for my tank pump out hose fitting, but now am wondering if I should have bought the black nylon, if there is a difference. It fit fine and I didn't think there would be much stress/pressure on it, so if the black nylon was stronger, I was thinking it probably doesn't matter. What are your opinions?

Thanks,

Freesail99 · #10 (**permalink**) 06-27-2007

Quote:

Originally Posted by JustinC25

I am almost finished with connecting up new hoses to my holding tank. I have one question though... How far do you really need to get the hose on the barb? Of course some are very tough and I actually sanded some of the barbs down a little to slide/force the hose on. Even then I could only get the hose maybe 1/3 to 1/2 way the length of the barb fitting. They don't seem to want to budge, but then again I don't want to have to deal with these again in the near future.

Also I noticed West Marine had two different types of nylon fittings for the tank. The white and then the black which cost 3-4x as much. I ended up buying the white for my tank pump out hose fitting, but now am wondering if I should have bought the black nylon, if there is a difference. It fit fine and I didn't think there would be much stress/pressure on it, so if the black nylon was stronger, I was thinking it probably doesn't matter. What are your opinions?

Thanks,

I've owned a winery for many years, we're always putting on hoses on barbed fittings. A heat gun works great. Heat up the first inch or so of the hose and then push it right on. Works very well.