Holding Tank Fittings

[Alptraveler]

Does anyone have any experience with installing npt threaded fittings into a holding tank? I need to install new threaded fittings into my new holding tank. I am getting conflicting info as to how tight is too tight. Polypropylene new tank, threaded and ready for the fittings. Some readings say hand tight + 2-3 xtra turns. The person who runs the business where I got the tank said..." tighten as as much you can tighten". I also read that if you tighten too much you can crack the tank(this tank was not cheap, not a situation I want to find myself in). I also don't want to be too conservative on tightening and end up having a leak since the fitting is at the bottom of the front of the tank, gravity pumpout(before I get criticism,  this tank is shoe horned into the v-berth and has a unique configuration. The enclosure around the tank does not allow fittings to protrude from the top, nor do I have the ability to be handy enough to reconfigure my v-berth to accommodate a new tank configuration....hence, staying with the original configurations).

1. Wrap Teflon tape 5-6x's around the threads, starting at the end

2. Hand tighten the fitting

3. How much further do I tighten the fittings(90° elbows)??? 

Thanks

[Peter McGowan]

The more Teflon wraps you use the fewer the threads you’ll engage before it’s hand tight.  Personally I use 3-4 wraps, hand tighten, then a turn or two with a wrench.  The number of turns with the wrench is inversely proportional to your grip strength when hand tightening :)  There’s no pressure in a holding tank system so you don’t need to be aggressive with it, just enough force that the Teflon is forced to fill in the gaps between the peaks and valleys of the fittings.  Pipe dope might be a better idea if you’re concerned about breaking the fittings as it’ll fill those gaps without as much force.

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[darin doherty]

What Peter said.

You don't have to crank on the fittings.  Snug, unfortunately, is relative to the person doing the snugging.

There is no real pressure to deal with in the holding tank unless someone blocks off the vent, and in my that case you are more likely to bust a seam due to the surface area.

Make sure the threads are good on both parts.

Without any sealant or tape, tighten the fitting by hand.

Make sure it seems to move easily before getting hand tight, no burrs or junk in the threads.

Mark this position on both pieces so you can realign them to the same point.

Unscrew them and apply thread paste, dope, or sealant.  You can use Teflon tape, but don't put too many wraps, thicker is not better.

Reinstall the fittings back to the alignment marks.

Tighten another half to full turn, especially if you need to align a fitting with a 90

If it feels to tight, it probably is.

Darin Dohery

P10 Cygnus.

Port Canaveral.

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[Last Resort]

I redid mine a few years back, and was taught a great trick by my friend who knew it....you take some very fine, but tough string (whipping twine works nice pulled apart into separate threads), cover it with a special white sealant goop (sorry, it's on the boat, maybe someone knows the brand name here), then wrap the gooped thread tightly within all the threads of the fitting, and watch the direction so you can start without it bulging up. Next, soak the whole fitting with the sealant goop and start threading the fitting in.  be sure the thread starts into the tank, otherwise pull it out and start again.  With the thread in and working, it should tighten up nicely before you have to be worried about going too far with it to damage anything. Will do a much better job than Teflon tape and last a lot longer!  Good luck!!!!   

[Last Resort]

I found it:   Loctite Thread Sealant with Teflon!   LOCTITE Thread Sealant with PTFE, Brush-Top Can, 473 ml, -51° C - 149° C/-59.8° F - 300.2° F AC144 (1527514) | Shop Thread Sealant | TENAQUIP

[Alptraveler]

Yup, found a different version of the same stuff...rectorseal tru-blu,ace hardware,small tube. Thnx

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[Last Resort]

good to hear and hopefully the tube is big enough for all the fittings as it takes quite a bit of product on each one :)  

if you missed it, another post (3 updates in 1 topic) here on your question mentioned that Teflon tape should NOT be used on tank fittings!

also, be sure to have a heat gun around when installing the new hoses :) 

[Alptraveler]

Thnx, I think I saw the posts you mentioned but will check again. I find it interesting that Miss Peggy says to ONLY use Teflon tape, others say tape + goop, others say goop ( I will take the size of goop I purchase into consideration after your response).

As you know, May in the Great Lakes is cold and the hoses will be stiff from sitting over the winter. We will warm the vberth with a heater while at port, engage a heat gun or hairdryer as well. We will add KY gel to make the hose slide on better, followed up with double clamps. Boat launch= May 16.

Now...let's hope that the new tank is an exact fit to the old since it was tight fitting in the 1st place.

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[Last Resort]

Should be good as there must have been others with the same refit :)  

BTW, are you planning any trips to the North Channel this summer...be great to meet!   We hope to be in the water by June 20th for our 60 days plus of live-a-board till Labour Day :)  

[Alptraveler]

We decided to hang out on the Lk Mich side this summer....Lake Charlevoix, Boyne, Beaver Island, Traverse City. It's  a LONG truck for us to even get to Le Chenoix's, eating up days of travel by being weathered in with smallcraft advisories. I tjimk we got stuck on BI for 5 days til the reef and straits were safe for travel. One boat tempted fate and broke their shrouds, another had their wife on the floor in fetal position for 6 hrs (we decided tomwait it out and consume.from the local brewery). We will tag team with our slip mates next summer up the the N.C. I will definitely try to coordinate our where- abouts. It would be nice to meet up with you and family.

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[Last Resort]

Well enjoy, and maybe someday we'll catch up :)   Good luck with the tank and hopefully things go smoothly.  Btw, I took out the 5' loop from the Y valve, as the Y valves are illegal in Canada anyway if not secured CLOSED permanently, and put in a straight hose to the Head from the tank with a backflow preventer just off of the tank in case that interests you.  

[Jeff Griglack]

Damn, I guess my system is really illegal in Canada. Mine has 3 y valves. I still haven't figured out why or quite how the system is supposed to work.

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[Dave Cole]

The tank wall where the threaded fitting enters should be thicker than the rest of the tank to withstand the pressure from the tapered fitting.  

otherwise it will be prone to cracking.   Only tighten it sufficiently to get a good seal and secure the hoses so they don't tend to rotate the fittings while underway.  I'd say hand tight, plus 1/3 turn, etc.

I do a fair amount of plumbing of various kinds and work with a group of mechanical guys who do large amounts of plumbing in industrial plants.  Where hundreds or thousands of feet of pipe installed on a ceiling, 30 feet off the ground is common.  

Rectorseal is ok, and I have used another brand of Teflon sealant that Menards sells in volume (forget the brand) but the guys I work with swear by Blue Monster products.   I talked to them after having some mixed results with other brands.  Since then I've used their tapes with great success on water lines for a low pressure boiler installation and natural gas lines.   Compared with most other tapes (many which failed), the other brands are simply poor in comparison.   If you are trying to save money on the thread sealant you are doing the wrong thing.   In this space you pretty much get what you pay for.

The really cheap white teflon pipe tapes are really cheap teflon pipe tape.  

I think a big roll of Blue Monster pipe tape is about $7.00 at Menards and it will do a large number of 1 1\2" and 2" joints. 

Their pipe seal compound is also really good.   Either should work well for your plastic to plastic threaded joints.  But I would go with the Blue Monster pipe tape.

What I found is that the other tapes I used couldn't compensate for the poor thread fit that is common now in many threaded fittings.   

The Blue Monster tape somehow addresses this issue.   The difference is really substantial.   

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[Alptraveler]

Thank you Dave! To address doing the job on the cheap is not what I was considering, especially after paying so.e decent $ for a really good tank. I will read up on the product(s) you mentioned. And yes, before I sent this post I WAS going to use good ole white Teflon tape, not being savvy that there were better products out there.

As far as the tank and the threaded females....the threaded area has a 1/4" square backing plate heat welded for the purpose of adding strength. 

The tank itself had only 3 straps holding it in place. I am taking xtra webbing to add to the security, I added 3x3 rubber pads at the front of the tank bottom(the kind that are used to control vibrations on washing machines) to control forward movement into the front knee wall. The actual pumpout hose will not be able to budge once the top board is in place since the fit will be tight. The air vent hose and hose from the toilet/vented loop is secured in the vberth with webbing as well.

Your suggestions were great reminders for me as we complete this task. I am self educating so I have a say in how I want "my project" to play out as I have recruited someone to help me and may be set in their old fashion ways of how they have done things FOR YEARS.

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[sides...@aol.com]

Was at the boat today and discovered a fuel leak that looks like it is coming from the aluminum tank.  I am in the beginning stages of removing the tank and would welcome any advice. I have read Last Resort’s post about getting it out, it helps a lot but if you have any pictures of the wood portion that was cut out and what you ended up patching it with would be appreciated. My partition wall has a lot mounted to it and I also have my a/c compressor located in the back of the lazerette.

I am also not sure if the tank can be repaired of if I will have a new one made. I am assuming that I will probably go with a new one.  If anyone has ordered one or has a drawing of the tank,  original maker or serial number it would help,  I have been referred to  and am considering Ezell industries a tank maker in Florida that does custom tanks with a pretty fast turn around.

Thanks,

Bob

Blue. Moon. 31-2

[Last Resort]

Bob, no to hijack this post, I posted your reply in my original Tank Removal posting!

[Alptraveler]

I just looked at your launch/out dates again....are you in education? Those dates are teacher vacation dates in Michigan. I know them well....before retirement. 

Will be in touch for a meet up in the NC with you and family hopefully next summer. Our travel mates are not traveling up there this summer, they have a wedding and when we were all hiking together in Tucson this winter 1 of them sustained a helicopter ride worthy injury. She is just able to put weight on both of her injuries....shattered knee cap and tib-fib fracture in 3 locations@ 2+ surgeries,both legs. We are pondering around our neck of the woods for the summer.

We also just got some engine work done recently and want to stick near'ish home port to "test" our engine work.

We decided we are gonna plug up our fittings with rubber stoppers and fill up our holding tank with water at home after we mount the fittings and before we install it on the boat.

We may need to tweak the angle a tad for the hoses but my pics of the old tank gives me a pretty close estimate.

Maybe I bring the old tank home, pwr wash it and try to sell it "as is" really cheap to someone around metro Detroit or near my boat??? There are always handy people who want to tackle a fix-up.

On Tue, Apr 4, 2023, 3:41 PM Last Resort <lastre...@gmail.com> wrote:

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[Alptraveler]

I think the valves are OK to have as long as you have them buttoned up with wire or clamp. When we have been boarded by the Coastguard they just make sure the tank is out of commission for direct dumping into the lake. They have never mentioned I need to rid of the valve. My boat has never seen saltwater, not sure why the valve is there except maybe in the 80's you could direct dump in the Great Lakes??? Maybe cuz the boats were made generically for fresh or salt...makes sense to me. I have seen many YouTube videos where people have multiple valves in their head system tho. I think...x2 at the tank and x1 at the head? Mine is simpler...x1 under the sink where if open it dumps into the lake,if closed it funnels to the tank. I just have it ziptied off in the closed position. Not sure of Canadian rules, ask your fellow Canadian sailors. Ask Last Resort,he responds to my questions and spends his summers in Canadian waters.

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[Alptraveler]

I will post when all is complete but I ended up getting Blue Monster from HD,both the tape and the dope. Gonna install the fittings here at home, rubber stop the fittings to simulate a fill up at the boat and just wait, wait to see if it leaks. I believe I ca  get a pretty darn close angle to what is needed by looking at my old tank fittings. I might have to tweak a tad, just a tad. It may seep in the boat but that will be a minor tightening vs a leak and hurry for a quick pump-out. Taking my simple transfer pump and hose with me in case I have to pump out any "testing fill water".

On Fri, Apr 7, 2023, 11:09 AM Dave Cole <dave...@gmail.com> wrote:

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[Last Resort]

Retired as for launch dates :)   Boat is 6hrs away, so it's always been 1 trip up, 1 home.   I never said or intended to infer that the Y valve had to be removed, I just did it for myself to take pressure off the Joker that seems to need replacing way too much!   Yes, clamping, or wiring it off is the way to go.   Great idea testing and installing the fittings at home. Don't forget some thin thread to wind into the dope, works wonders :)   Good luck and maybe we'll catch up next year :)