Replacing Sanitation Hoses & Fittings - Use of Sealant or Gaskets?

[jbmia]

With research, recommendations, and Peggy's book, I'm currently planning and acquiring components for the replacement of the sanitation hoses in a 2005 Beneteau 323 with the original Vetus holding tank. I'm going with the Raritan Saniflex. Since the original tank fittings seem to be loose and caked with old sealant, I'm going to replace them as well. I've purchased replacements from Beneteau parts department (see attached). My question is this.. given the tank is likely polyethylene and the fittings, nuts, and flanges are nylon, should I be applying any kind of sealant beyond the compression fit to keep odors in the tank? An o-ring or gasket of some sort? Or nothing needed? If sealant, what kind of sealant would be recommended? And where? On the inside between the top of the tank and the inside flange like it currently appears to be? I'd appreciate any guidance here...

 

[Ralph Johnstone]

If I'm looking at this fitting correctly, it will not seal against the interior tank wall with a gasket due to the bevel of the flange.

Furthermore, I would NOT use any form of gasket below the water line in a holding tank as it is likely to leak as the tank bulges when it fills. With this particular fitting, it would be 100% guaranteed to leak the first time the tank fills.

The threads on this fitting are straight threads (NPS) and must be sealed with teflon tape first and then covered with a layer of Permatex #2. However, this applies to above water level threads ONLY. Do not use NPS threads below the water line as they will eventually leak.

It doesn't appear as if you are off to a good start right from the get go. My suggestion would be to photograph your holding tank installation from several angles to let the group see what can be salvaged that will not leak.

 

[jbmia]

Hmm…. I thought I was off to a good start just by starting here.. ;-).

Heres the top of the tank (attached image). One side is the input from the head. Other side is the output to macerator. Middle is the vent. These fittings are on top and should be above the waterline as long as there’s no overflow. Pumpout is on bottom and that fitting is not being replaced.

The flange you’ve pointed to that would contact and be flush with the interior ceiling of the tank is flat if it doesn’t appear so in the first image. These are OEM replacements so I would hope they’d work. My question was more of a double check on ensuring they’re installed with a good seal. Especially between that flange surface and inside of the tank… Permatex on flange surface as well or just threads? 4200?

Thoughts?

 

[Peggie Hall HeadMistress]

Use only teflon tape on the threads, NO sealant or gasket. You may need a gasket (rubber) between the fitting and the tank wall.

--Peggie

 

[Peggie Hall HeadMistress]

Question: I keep reading that the fittings in this tank are NPS. Is that specific to Beneteau? Or maybe Vetus? 'Cuz US thread-barb tank fittings have been NPT standard for longer than I've been workng in marine sanitation.

--Peggie

 

[jbmia]

They do appear to be NPS. When I thread the nut on, it does not get tighter... The flange will only thread till it bottoms out at the base of the flange side. Unfortunately, I don't have answers to your questions. Would the fact that these are NPS impact the your suggestions above?

 

[Peggie Hall HeadMistress]

Teflon tape seals threads, so it shouldn't matter whether the threads are NPT or NPS. In fact the tape should be even more important if the fittings don't tighten as you thread them in...which does eliminate any risk of OVER tightening them. I'm not sure about using Permatex 'cuz sealants on threaded fittings usually aren't recommended because they make removing them very difficult if not impossible without damage to the fitting. This is the first time I've seen a rigid Vetus tank...I didn't know Vetus makes any tanks but bladders.

--Peggie (still learning after 35 years in this business)

 

[jbmia]

I picked up some nitrile gaskets on Amazon that should fit the flange... this one look okay?

 

[Ralph Johnstone]

The flange you’ve pointed to that would contact and be flush with the interior ceiling of the tank is flat if it doesn’t appear so in the first image.

Yipes. Looks bevelled to to me but if you have it in hand, then flat it is. I guess it doesn't help with my being blind in one eye and can't see out of the other.

As for a gasket, you could use either a soft rubber gasket or Permatex #2 alone for a gasket. It's a non pressurized seal so you can live without the gasket if so desired. Permatex #2 does not harden so it can be removed slowly even after being in place for years. Dissolves with methyl or ethyl alcohol.

As far as the NPS threads go, the one thread of concern is shown as :

This is an NPS and not an NPT which is almost certain to leak. If it were anything else except holding tank contents, go ahead and give it a try. In this case, a definite no, no.

I know Peggie is going to hammer me for sure on this one but "be sure to apply several wraps of teflon tape in a CW direction and then, a light coat of Permatex #2 in a CC direction for a guaranteed seal on an NPS thread. The real truth here is that teflon thread is not a good thread sealant and is used only because it's neat, clean and tidy. Paste thread sealant does a far better job but is sloppy, miserable, and gets all over every surface within one or two city blocks. You'll see what I mean as soon as you open the Permatex #2. Horrible to work with but guaranteed to seal when applied correctly.

When it comes to large sloppy NPS threads, it seems that a mix of Permatex #2 and teflon thread do a better job of sealing on the threads which are NOT intended to seal.

NPS threads are always used for applying force to gasketed surfaces. You can imagine the problem of using an NPT thread if it either wasn't tight enough or was too tight to accommodate the required force on the gasket.

 

[jbmia]

Thanks for the insight Peggy and Ralph.

Yep, the flange is flat..

I went ahead and dove into the project this afternoon and have disconnected one of the hoses from the top of the tank and completely removed the pump out hose to the bottom of the tank. To speak to the NPS threads leaking, the question of using Permatex on the threads and as a gasket, the reality is that with the stiff nature of the old Trident 101, these fittings are just snapping at the top with little effort. Whether these are original or not, I'm not sure, but some sort of white sealant was used... (pic attached). So, at the end of the day, I'm not sure it matters if these need to be easily disassembled or not...

The Trident 101 was a bear to remove from the base of the tank given it's so old and stiff.. I did end up removing the hose barb at the base (for the pumpout hose) and it's threaded directly into the base of the tank with the interior bottom of the tank having a molded in nut (see pic). The bottom of the tank shows the busted off flange and some old sealant from the attached pic of the fitting and the hose.

So, I have a question about the this bronze(?) hose barb... I'd like to replace it since it appears to be somewhat pitted on the inside and I'd rather not have to think about this thing leaking at some point.. It obviously fits the 1.5" Trident hose on the barb side.. and measuring from the peaks of the threads with a digital caliper it appears exactly 1 7/8" and has a 1/8" rubber gasket that fits between it and the tank... I'm guessing by the looks of it that it's also NPS... but not 100% sure.. with the tank threaded to match, I'm guessing that's important. I'm going to try and hunt down a replacement, but would appreciate any suggestions.

I've also attached a pic of the tank.. apparently made by a company named ANISA. There appears to be very little information on the manufacturer. Beneteau lists the tank as "obsolete". The tank does appear to be solid and stout and it usable condition.

Much appreciation for any other comments and suggestions.

jbmia

 

[Ralph Johnstone]

So, I have a question about the this bronze(?) hose barb... I'd like to replace it since it appears to be somewhat pitted on the inside and I'd rather not have to think about this thing leaking at some point..

All fittings on the tank should be plastic i.e. nylon or PVC.

I'm guessing by the looks of it that it's also NPS... but not 100% sure.. with the tank threaded to match

Anytime it is used to tighten down on a gasket, the thread will be NPS.

I was going to mention :

 

[Tally Ho]

I just want to clarify one thing…

In this photo, it looks like the circled flange is threaded on upside down.

The elbow is inserted into the tank (threads inside the tank), and you need to thread the flange on though anotherho,e in the tank. Then the top flange is put over the barbed end and tightened down against the tank.

There were some questions about the lower flange not being flat against the tank…and it will be if it is threaded on correctly.



Greg

 

[Ward H]

I just want to clarify one thing…

In this photo, it looks like the circled flange is threaded on upside down.

The elbow is inserted into the tank (threads inside the tank), and you need to thread the flange on though anotherho,e in the tank. Then the top flange is put over the barbed end and tightened down against the tank.

There were some questions about the lower flange not being flat against the tank…and it will be if it is threaded on correctly.

View attachment 224164

Greg

Greg, I agree and was just starting a post to say the same thing but you beat me to it.

 

[jbmia]

I initially thought the flange should thread on the suggested way as well.. but there appears to be a stop in the base that won't allow it thread that way.. when you thread it the way I have it, it threads on and stops at that end where this 'stop' doesn't allow it to be threaded further... I've attached a few close up pics, but it's kind of hard to see without actually trying to thread it on yourself.. I've also taken a pic of one of one of the old ones currently in place showing that the way it's threaded here in the pics is the way its intended... go figure.. must be a euro or Beneteau thing...

You'll also note in that pic of the currently installed one that theres a pick up tube heading down (this is for the macerator)... the replacement pick up tube is pvc and the fitting is nylon.. it appears the pick up tube just snugs up inside.. no threads... any suggestions on gluing it in place? will pvc cement work on nylon? other cement or sealant?

Also, anybody have any suggestions on that brass hose adapter at the base? I get that it should be plastic or pvc etc, but fwiw, this is the OEM fitting... In any event, I took more measurements.. it does appear to be a parallel thread.. max thread diameter measure 1 7/8", but it could be metric... nearest I can measure is 47.5 at peak of threads, 45mm inside grooves, and 2mm pitch (thread height to thread height).. I can't find anything that matches this fitting some any insight or suggestions would be appreciated.. PVC fitting spec don't seem to give thread details since they're all thread to fit each other.. the thread is definitely larger than the black nylon adapters that go on top... I could put this one back in, it appears solid, but some pitting is noted.. it will likely last a few more years, but I'd rather just replace it if I can find a suitable replacement and be done with it... appreciate any direction...

 

[Tally Ho]

Ok…maybe so, but it would be unusual to have the small “lugs” in the hole..

note how the flange is oriented on the green tank photo…I believe it should be oriented like that (with the lugs away from the hole in the tank…regardless of whether it is inside or outside of the tank.



It is also interesting that some of the hoses attachments have the gasketed flange on the outside (and I presume the circled one) has it on the inside.

Greg

 

[jbmia]

Yep... that one, the vent fitting, is different.. it has it's own built in flange... the actual vent outlet has an ID of slightly less than 3/8".. really small.. so I'm thinking of rigging up something else.. the threads are 1 1/4" so I'm thinking I can replace this one with a 1" adapter, just haven't looked yet.

I sent an email to the local Beneteau parts guy on that bronze fitting asking him to check with his contacts in S. Carolina... Hopefully he'll have something useful to report.

 

[Tally Ho]

That one looks “right” to me….but I am not French and who knows what Bene was thinking.

I still think the other one would work if you reversed the orientation of the inside flange to look like the one with the integral flange.



Good luck…plumbing is always fun on a boat

Greg

 

[jbmia]

Thanks Greg. It won't thread the other way.... At this point, giving these seem to be just popping off under light pressure, I'm thinking I might just switch these out for standard fittings... The two large holes are just over 2" and the center vent hole is just over 1 3/8".

 

[Tally Ho]

Sounds like a burr or something in the thread…but like I said…who knows.

Sounds like you are getting a handle on it.

Greg

 

[jbmia]

Another question for the group.. If I were to abandon the Beneteau fittings, would something like the thru hull in the link below work? These are nylon, include the flange and the nut, and seem to be the right size... I'd appreciate any other suggestions if these arent fit for purpose..

1-1/2" Nylon 90° Thru-Hull with Barb

Glass-Filled Nylon Hose Size 1-1/2" Dimensions Flange O.D.: 2-3/8" Thread Length: 1-5/8" Barb Length: 1-1/2" Overall Length: 4" Cut Out: 1-1/2" Max Hull Thickness 1" Proposition 65 Warnings Website - Your right to know (ca.gov)

www.whitecapmarineproducts.com