When the new holding tank arrived at the marina office via UPS, it was a heavy monster. I took the 28-gallon beauty out of the box and showed Windy just how thick the polyethylene was. Surely we were one installation away from an odor-free vessel.
Not long after I installed the new tank we began to notice the smell.
“Maybe it is residual from the old tank.”
A day passed.
“Are you sure you cleaned up really well from the old tank?”
A week passed.
“Did you forget to tighten a hose clamp?”
We hadn’t needlessly replaced the old broken tank—it was cracked and the flanges where two of the fittings attached were leaking—but could we really have made things worse?
Then the smell became unbearable. What the heck?
I checked and rechecked everything, again. I bought some microbe pellets at West Marine that are supposed to naturally keep odor in check. Things seemed to get worse, and each of us, in turn, began to miss our old leaky tank.
Then I found the problem.
Our brand new, nearly $300 Todd tank was defective. The welded polyethylene flange at the top of the tank, threaded for the inspection port, was leaking. I called Todd. They seem like nice folks, but they were not keen on discussing tank problems over the phone, they wouldn’t even hear me out. I was told to take pictures of the problem and send them a description and they’d get back to me within five business days. Nonsense. [Ed: note that a previous version of this post indicated that I talked to Todd’s Mexico and Central American representatives, E&P Marine, but that was incorrect, I spoke with Todd customer service directly.]
So I turned to my friends at Google and learned everything there is to know about repairing polyethylene. The sealants we commonly use aboard don’t work on polyethylene, not even the tenacious polyurethanes like 3M’s 5200. Learning how to seal and repair the material would come in handy as everything is made with the stuff these days, from our kayak to our new Portland Pudgy dinghy.
It turns out there are several different approaches, but I went with Gougeon Brothers’ G/flex epoxy. So long as the surface is prepared correctly, the stuff sticks to and seals polyethylene very well. I abraded the crevice with a Dremel, cleaned it with rubbing alcohol, heat treated it with a butane torch, and then mixed and applied the epoxy. A couple weeks later, I am happy to report that the bond is strong and the head odor is completely gone.
While I’m on the subject, I’ll pass along a tip we learned from someone before heading out: oil and vinegar are your toilet’s friends. We keep a spray bottle of oil and vinegar at hand and we shake it up and give a couple squirts with each flush. The vinegar is a sanitizer that keeps hoses from calcifying and the oil helps lubricate the pump. Use a cheap vegetable oil and plain white vinegar, anything fancier and you risk developing an unwanted negative association that will put a damper on your salad cravings.