Poly Tanks and Sealant

[Christian Van H]

Hi All! I'm installing my Ronco poly tanks for my freshwater system this weekend (3 X 50 Gal.), and I just read this on Ronco's website:

"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."

I was planning on using a little Teflon thread sealant... Has anyone installed their nylon fittings into their tanks dry like their instructions specify? I know these fittings are NPT (tapered), but these connections are tough to get to after all is in. Thanks, Chris

[svHyLyte]

Poly tank fittings seal, in part, by the action of galling. Any material that prevents that also prevents a seal. The material used in Ronco tanks and fittings are a low energy plastic that makes bonding difficult or nearly impossible. The only known bonding agent that has proven effective is Scotch-WeldTM DP-8005, a two-part, acrylic-based, structural plastic adhesive designed to structurally bond polyolefins.

[Christian Van H]

Thank you svHyLyte. That make perfect sense. I do have the Scotch-Weld and the gun, but I would REALLY worry about a repair if I ever broke off a fitting after bonding with that. I think you are right, and I'll probably go with just a dry fit. Hey, no matter our other differences, I have read your posts on all things sailboat, and I know you know your stuff!

BTW, you probably already know this, but the difference between Scotch-Weld 8005 and 8010 is just the pot time...5 vs. 10 minutes. Took me a while to figure this out!

[perchance]

Over tightening will split the female fitting. How do I know? The PO did just that but the local chandlery assures me the can rapair it.

[speedoo]

Chris, I was looking at Ronco tanks a few years back but was concerned about the lack of baffles. Are you planning to go offshore with yours, and if so is the lack of baffles a concern?

[Christian Van H]

Hi Speedoo! I think I would be if the tanks were any bigger. These are all long and thin, with all sides well supported. I am looking at buying a 50 Gal. or so Black water tank soon though, and because of its shape I will be looking for a baffled tank.

[Christian Van H]

Originally Posted by perchance

Over tightening will split the female fitting. How do I know? The PO did just that but the local chandlery assures me the can rapair it.

That Scotch-Weld svHyLyte mentioned might be the ticket, if you wanted to self repair.

[Chief Engineer]

Follow the manufaturers' directions.

Just like exhaust manifolds like Osco and Barr tell you NOT to put teflon tape on the plugs....

Or the instructions on oil filters....tighten 3/4 to one turn after gasket contacts base.

The key is "tapered" pip threads

[speedoo]

Originally Posted by Christian Van H

Hi Speedoo! I think I would be if the tanks were any bigger. These are all long and thin, with all sides well supported. I am looking at buying a 50 Gal. or so Black water tank soon though, and because of its shape I will be looking for a baffled tank.

Hey Chris!

How about an update on your water tanks and black water tank. I will soon be doing mine and I still have not decided whether to go with Ronco or have some built with baffles.

Really need advice based on experience!