Water Tank Thread Sealer

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Hello fellow Cbrats,

How do you property seal the nylon fittings that connect to the 20 gallon on board water tank? I pulled the water tank out and it appears a leak is coming from either the air gap fitting or the pump hose fitting.

I tried using thread tape but that didn't work :( Of course I realized this after reinstalling the tank, the line to the water pump, air gap tube . So I pulled the tank out again and want to make sure I do it right this time.

I'm guessing the sealer needs to be food grade because it would be exposed to sink water? I won't be drinking the sink water so maybe this isn't important?

Marine Silicon was my next thought but the directions say the silicon is for above water application only.

Permatrex thread sealant was another thought but it's not food grade.

After pulling out the water tank, I realized the water lines need to be replaced because they are gross and full of nasty stuff. I am now replacing the water line all the way to the sink.

:thup
 
If the fitting is leaking chances are that it has been damaged. I prefer to use brass fittings when possible. Using Teflon tape works, if you apply it properly so it does not 'unwind"--hold the fitting in the left hand, and put the tape on the top, going to the left, unwinding off the inside of the spool, around the bottom and then up the right side.

IMG_1685-300x225.jpg

Occasionally on the C Dory the builder has used British standard threads--usually in the showers. In that case there is enough pitch difference between the American Standard, and B ST, that you have difficulty getting a good seal. C Dory put some Bostic sealant on it--doesn't work well.

There is the teflon plumbers goop, which works well.

However, when I have had problems, I could not fix any other way, I used the Permatex Form- a- Gasket #2, soft, non hardening. Started doing that almost 50 years ago--and no problems...the gasket material should not have any significant contacts with the water.
 
My memory said that nothing should be used on nylon threaded fittings, but I decided to double check before saying anything.

I looked on Ronco Plastics' website. They are a long time family plastic tank company who are well thought of. Here is what they say:

Plastic tank connections are designed to seal dry. Compounds such as sealants, pipe dopes, greases, petroleum jellies, glues or adhesives are not to be used. Normally, hand tightening will provide adequate seal. On occasion, a slight tightening with a wrench may be required. To avoid damage to seal fittings, do not apply excessive force. Do not exceed 1/4 turn after hand tightening.

Note that this doesn't stop some boat or RV installers from gooping up the fittings.

A couple of other notes based on the stock tank that was in my 22.

1) These tanks are supposed to be supported fully on the bottom. My tank was installed such that the outboard side was "hanging" on the chine and the only other support was on the inboard edge. Easy to solve with a 1/2" platform on the sole.

2) Mine wasn't leaking when I removed it, but did start leaking subsequently (before reinstalling though). What had happened was that the spin weld failed (the fittings are installed in the tank by spin welding - that's that bit of white plastic that looks like hardened liquid plastic around the fittings). So just something to check in case it isn't the fitting.

If the male fittings were "glopped up" with something know that new ones are quite inexpensive (<$5) so you could get new ones (I'm speaking of the fitting that goes into the female boss that's spin-welded into the tank).
 
thataway":166lg0ox said:
If the fitting is leaking chances are that it has been damaged. I prefer to use brass fittings when possible. Using Teflon tape works, if you apply it properly so it does not 'unwind"--hold the fitting in the left hand, and put the tape on the top, going to the left, unwinding off the inside of the spool, around the bottom and then up the right side.

IMG_1685-300x225.jpg

Occasionally on the C Dory the builder has used British standard threads--usually in the showers. In that case there is enough pitch difference between the American Standard, and B ST, that you have difficulty getting a good seal. C Dory put some Bostic sealant on it--doesn't work well.


There is the teflon plumbers goop, which works well.

However, when I have had problems, I could not fix any other way, I used the Permatex Form- a- Gasket #2, soft, non hardening. Started doing that almost 50 years ago--and no problems...the gasket material should not have any significant contacts with the water.
Click to expand...

or a huge glob of Bostic! LOL
 
Thataway, Sunbeam - you guys are terrific. I can't thank you enough for you're advice.

I reinstalled the water tank last night with no thread tape or sealer and there is still a leak. So here we go again, attempt #3. I applied a liberal amount of silicon to each fitting, will let it sit overnight and give it another go tomorrow. Even though each fitting screws on properly, the nylon threads may be the issue here.

I haven't gone on long excursions yet so I don't know if I need 20 gallons of fresh water. It seems it would take a couple of days of foot pumping to empty the tank!

If this last attempt doesn't work, plan B. I'm not sure what my plan B is yet. Replace with another factory tank? Downsize to a smaller water tank?

Any thoughts on plan B?

:thup
 
ThumbsUp":2ejwj1wk said:
Any thoughts on plan B?

:thup
Click to expand...

Here's one idea: When my tank sprung a leak at the fitting (spin weld failure), I already knew I might want to do something different with the water tank (at the least a dip tube vs. the supply feed on the bottom, but maybe also a different location or size). But I also wanted to go boating and have water - since that experience would help form my ultimate plan.

So I hooked up a quick and easy "modular" system just before a long trip. That was two years ago and it has worked so well I haven't done anything different yet! I still may, but there is no rush. I can see where my "system" might work well for someone who doesn't always need the full ~20 gallons. Not to say it's ultimate or anything, but an idea (but tank spin welded fittings can also be repaired; I just didn't want to repair my tank and gave it to a friend who wanted it).

If you go to this link then scroll down about 2/3 of the page, you'll see my plan with photos and descriptions. I think I also added some additional info on the next page in the thread. When I'm using the system, there is no indication it's not a "real" tank (I have a foot pump not an electric pump).

http://www.c-brats.com/viewtopic.php?t= ... c&start=90
 
There are very few sealant products that will "stick" to plastics. Here is a product that even " sticks " to Starboard Kingboard. Sudbury Elastomeric Sealant, manufacturer says can be used on plastics. Above or below the waterline. Many boatyards apply 5200 to plastic fittings, but this product label says not to be used plastics.
The problem with silicone is that it seems to lube the threads, and it is to easy to over tighten the threads stripping them.
I have been using this product for some time, it does stick very well. The only negative is that it skins very quickly, so don't use where you will need to be fingering to a smooth finish.
alan
 
Really appreciate the comments Sunbeam and Sanjuanderer! I am going to re-install the water tank tonight for attempt #3. Wish me luck!

:thup
 
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