Plumbing holding tank connectors

[vladkri]

Greetings. I'm going to install brand new custom made plastic (PET) holding tank. The manufacturer provided me with various PVC thread-to-barb connectors which I'm supposed to screw into threaded holes in the tank. The one I'm worried most is the pump-out port at the very bottom of the tank. How do I ensure it 100% will not leak? For the threaded part they recommended teflon tape, but I had rather poor luck with it in other plumbing applications. So what else can be used? Some sort of plumber's thread sealant? 3M 4200? What about barb side? The old plumbing has some sort of white sealant on barb side. Now, I'd rather retain ability to undo both connections in the future. All ports are 1.5 inch. Thanks.

[peghall]

Wrapping the threads in Teflon tape has always worked for me...it's important to use enough--several wraps. Tank fittings--at least all those in the US--are NPT standard, which means they're slightly tapered--TOO slightly to be noticeable with the naked eye in such a short amount of material. This makes it very important to avoid OVER-tightening them...use no more than a quarter turn past hand tight and maybe even less. Just make it snug.

As for the barb end which may or may be smooth instead of actually barbed)...No sealant should be used. Warming the hose--be careful not to overheat if you use a heat gun...I always used blow dryer--and lubricating (the industry has always recommended dish washing liquid (Dawn or similar...KY is a water soluble surgical jelly that's exceptionally slippery and dries out) on both the inside of the hose and the outside of the fitting will make it much easier easier to put the hose on the fitting and will allow you to remove them if necessary...warming makes that easier too.

All sanitation hose connections should be double clamped, with screws 180 degrees apart...or at least 90 degrees if access makes 180 impossible.


--Peggie

[rwidman]

Teflon tape is pretty much a standard in the plumbing field. If you are having trouble with it, you are doing it wrong. Left handed people sometimes apply it in the wrong direction. It goes on in the direction where threading the fitting in tightens the tape. And yes, use several wraps. Five or so.

As Peggie posted, no sealant on the barbed connectors. I like to use a product called "radiator hose lubricant" which can be found in auto parts stores. West Marine sells it as well as "hose lubricant". The lubricant makes it easier to install the hose and easier to remove it a few years from now. Your hose clamps will hold it in place until that time comes.

[cal40john]

Too late for you, but I bought a tank with only top openings. A pick up PVC tube goes into the tank from the top. Similar to this.

https://www.defender.com/product.jsp?id=679342

[vladkri]

Originally Posted by cal40john

Too late for you, but I bought a tank with only top openings. A pick up PVC tube goes into the tank from the top. Similar to this.

https://www.defender.com/product.jsp?id=679342

Darn it. I'm sure they could weld pickup tube from the top. Never occurred to me. Oh well. About teflon tape, just to confirm, it's several layers on each mm of the thread or several overlapping wraps covering entire thread except first few?

[Glassdog]

On my recent overhaul of plumbing with new holding tank and all new fittings I use yellow Teflon tape (Spect for gas as it is thicker) topped with a thin layer of plumbers pipe sealant to ensure that all joints are odor and leak free. My motto on all things Marine: proactive, instead of reactive :-)

[rwidman]

Originally Posted by vladkri

Darn it. I'm sure they could weld pickup tube from the top. Never occurred to me. Oh well. About teflon tape, just to confirm, it's several layers on each mm of the thread or several overlapping wraps covering entire thread except first few?

Since it's a relatively large fitting, you want to use the wide tape. Start at the end and wrap overlapping wraps up as far as the fitting will screw into the tank.

If you would rather, you can use pipe dope instead of tape as long as you use the kind appropriate for plastic pipe.

I suspect you could find instructions on youtube on how to apply Teflon tape.

[meirriba]

Originally Posted by vladkri

Greetings. I'm going to install brand new custom made plastic (PET) holding tank. The manufacturer provided me with various PVC thread-to-barb connectors which I'm supposed to screw into threaded holes in the tank. The one I'm worried most is the pump-out port at the very bottom of the tank. How do I ensure it 100% will not leak? For the threaded part they recommended teflon tape, but I had rather poor luck with it in other plumbing applications. So what else can be used? Some sort of plumber's thread sealant? 3M 4200? What about barb side? The old plumbing has some sort of white sealant on barb side. Now, I'd rather retain ability to undo both connections in the future. All ports are 1.5 inch. Thanks.

Pump out port at the bottom?
AFAIK the pump out is mounted usually at the top while at the bottom you have the hose that goes into thd sea (tank emptied by gravitation).

[Ninedotsix]

Originally Posted by cal40john

Too late for you, but I bought a tank with only top openings. A pick up PVC tube goes into the tank from the top. Similar to this.

https://www.defender.com/product.jsp?id=679342

I agree with this, and ordered a tank without any threaded connections below the tank fluid level.
Installed a lift tube I made, much like the one in the Defender link.
It was my response to the only trouble I’d had with the original tank, when the spun welded joint the mfg installed at the tank bottom failed the weld, and leaked into the bilge (probably 35 years after build).
Most unsavory condition to find returning after a few weeks away from the boat.
I use Loctite 592 white aneorobic paste on plastic and precision metal threads, and Teflon only on common carbon steel, to improve fit up, applying tape over a coat of Gasoila thread sealant.
You’ll find many opinions on what’s “right” and what works “best”.
Happy Day
9.6

[peghall]

Originally Posted by vladkri

Darn it. I'm sure they could weld pickup tube from the top. Never occurred to me. Oh well. About teflon tape, just to confirm, it's several layers on each mm of the thread or several overlapping wraps covering entire thread except first few?

Several overlapping wraps that can cover all the threads..or all but the first few.

About that tank discharge fitting... thanks to a li'l gadget called the Uniseal UNISEAL it's actually pretty easy to install a new discharge fitting in the top of the tank if you're even a little handy with a hole saw or know someone who is. The new hole in the top of the tank should be above the deepest part of the tank or the low end if the tank has a flat bottom.

The Uniseal is actually just a rubber grommet that, when sized correctly for the hole in the tank and the PVC pipe that will become the pickup tube, DOES NOT LEAK unless there's side-side or front-back stress from a hose. I recommend you call 'em to order one instead of buying it on the net so you can be sure of getting the correct size hole and grommet and also so they can answer your questions.

You'll also need a piece of PVC pipe that has a 1.5" OUTER Diameter (to fit tightly inside 1.5" hose. It should be long enough to touch the bottom plus enough more to become the hose fitting. You'll cut the bottom end at about a 25 degree angle...any shallower can trap TP etc under it, any sharper leaves too much in the tank. That's all there is to it.

-Peggie

[Dougtiff]

So Peggy, i thought a 1/4" wall thickness on a holding tank didn't need a pickup tube, that the tank is strong enough to handle the pump out suction, without collapsing, no ?

[cal40john]

Originally Posted by Dougtiff

So Peggy, i thought a 1/4" wall thickness on a holding tank didn't need a pickup tube, that the tank is strong enough to handle the pump out suction, without collapsing, no ?

Can you explain your thoughts more? What does wall thickness have to do with not needing a pickup tube?

[vladkri]

Originally Posted by Ninedotsix

I use Loctite 592 white aneorobic paste on plastic and precision metal threads, and Teflon only on common carbon steel, to improve fit up, applying tape over a coat of Gasoila thread sealant.
You’ll find many opinions on what’s “right” and what works “best”.
Happy Day
9.6

Henkel Web site says 592 is unsuitable for plastic piping.

[peghall]

You're confusing a pickup tube--aka "diptube"-- with what I suspect may be a pressure relief valve . However neither one has anything to do with tank wall thickness.

Many tank discharge fittings are at the bottom of a tank...the pumpout line is on the outside of the tank and goes from that fitting up to the deck pumpout

fitting. When a tank discharge fitting is on the top of the tank--which a lot of owners prefer because it doesn't leave any standing sewage in the pumpout line--it's necessary to install a tube INside the tank that goes to the bottom of it.

As for tank wall thickness, 3/8" is strong enough to support the weight of the contents without flexing or bulging, but most tank mfrs recommend supporting a .25" tank on all sides. However, a particularly strong pumpout pulling against a blocked vent can even implode a stainless steel tank.


--Peggie

[vladkri]

Anyone had experience with Permatex Thread Sealant with
PTFE?