Sealant for Polyethylene Water Tanks

[Rob19574]

Hi all - My inspection hatches on my Polyethylene water tanks leak where the they screw into the tank. Is there any type of sealant out there I could use to seal the inspection hatches against the polyethylene tank wall? I checked the archives and could not find anything. Looks like I may need to make a rubber gasket but a sealant would be much easier.

Thanks and appreciate the insight.

- Rob

 

[Ron20324]

Maybe an O ring or two?

 

[Wally]

tanks

I have a Cat 36; 3 water tanks. All leak around the plates. I've found that If you don't fill them way up they leak much less. It seems the tanks expand if really filled, causing the "top" to dome, and the plate looses it's "seal". (I put "seal" in quotes because it's really hard to get anything to stick to poly).
W

 

[RichH]

Nothing sticks to polyethylene very well, so that rules out most 'sealants'. What will usually work is a combo of soft rubber gasketing with a wee bit of 'sealant' to take up the normal irregularities of the polyethylenes surface. Go to a 'gasket shop' (sometimes listed as 'rubber supplier - sheet') and ask for a soft rubber (Buna, etc.) with a 'durometer' (scale of rubber softness) @ 40 or less. They may also have 'foam rubber gasketing' such as "Santoprene". If you do use a 'sealant' the trick is to apply the sealant, the only partly press the mating parts together, let the sealant parlty cure for several hours, then apply full strain on the nuts, studs, etc. ... otherwise if you apply pressure too soon you will only 'squeeze-out' all the sealant.

 

[Peggie Hall HeadMistress]

Rubber O-rings...

Your inspection ports should have had them originally...if they're no longer there, replace 'em. Any poly tank mfr will have 'em or can put you onto a source. Try Ronco Plastics first (Dave...you wanna check on this for 'em?).

 

[Peggie Hall HeadMistress]

Wally...

Wally, if your tank sidewalls bulge when it's filled, it's an indication that either the walls are too thin to support the weight of the contents (water & waste weigh 8.333 lbs/gal), or it's not adequately vented and becoming pressurized. If the top, which isn't carrying any weight, bulges, that has to be a venting issue.

Catalina use Ronco tanks, which are top quality and definitely thick enough to support the water...which leaves the vent. Catalina used to vents their tanks through a very small slit in a rail stanchion (they may still do it on some boats)...the vents--especially holding tank vents, but water tanks too--are easily clogged. but don't really provide enough air flow even if they aren't. So improving the ventilation to your tank should end the bulging.

 

[Rob19574]

thanks all - appreciate the advice and tips. I will try to fabricate a gasket.

 

[jibes138]

Pickup Truck Cap Gasket

They use an adhesive soft foam rubber tape to seal the caps on pick up trucks. Check out anyplace they sell caps and you can get a roll of it. This stuff works great, it is soft enough to form to any uneven shape and one compressed is very water tight. The adhesive holds it in position while it is being tightened.