J/42 Tank leaks and Zinc survey
Ivan Getting, Kittwake, September 2007
Thank you to all of you for responding to my inquiry about holding tank and zinc problems on J/42s. About a dozen were received. Below is an approximating compilation your responses with some comments of my own added (in Itallics).
No one else reported holding tank leaks at these fittings. One reported nylon fittings rather than Marlon fittings. One reported gray fittings (could well be Marlon). So far I seem to be the only one to have sewage dumped into my bilge. I plan to replace the aft holding tank and use matching tapered pipe thread fittings in the ports. After the forward tank let go I cannot rest easy with those Marlon fittings in my aft tank.
Inspection (cleanout) Ports
Several people reported leaks at the water and/or holding tank inspection ports. This results from the manufacturer having used a fairly soft, round cross section seal (O-ring style) without providing any radial constrain for the outside of the seal. As the cap is tightened the seal extrudes outward prior to forming a good seal. This frustrates any further hope of making a seal. Less torque leaks anyway. My solution, and that of several others, has been to wrap the machine threads of the cap with Teflon thread sealant tape (or to use some other thread sealant). The parallel threads are not designed to seal, but they do with enough tape. Too much tape could stretch the female threaded insert, so be careful. I tighten mine gently with a very large pair of slip-joint pliers (Channel Lock, $35) which grip the protrusions on the edge of the cap and then do not remove them unless necessary.
Aft Head Odors
Unpleasant odors in the cockpit were reported by several people. The aft holding tank does emit odiferous air out its vent as material is pumped into the tank. This can lead to an unpleasant odor in the cockpit area for a while, but it typically dissipates rapidly and ceases when the head is no longer being pumped. When I first noticed it I was quite concerned that the aft holding tank was leaking. Fortunately, it was not.
My aft head produces a noxious order like rotten eggs if it has not been pumped for as little as one day and used only for urine. We purge the exit hose with 10-15 pump strokes. The cause of this unpleasantness remains a mystery. It does no happen with the forward head.
Zinc life was highly variable. Offshore conditions lead to the longest zinc life. Warm water and/or specific harbors seemed to produce the shortest zinc lifetimes. Reports are (crudely) tabulated below:
Zinc Life (months) Number of Reports
12 -36 2
My zinc life is 2-3 month during summer cruising in the Pacific Northwest, including Canada, and the full 8 months the boat lies unused in the marina during the winter. The short life during the summer requires diving under the boat to change zincs under inconvenient circumstances on longer cruises.
Two people reported having their fuel tank rot out on the bottom where it sat in water due to poor drainage and wet residual sawdust chips left under the tank. I sure hope this is not a common event!
I have an auxiliary bladder fuel tank which dumps into the main tank through a valve mounted in a plate on the top surface of the main tank. This plate appears to have installed in a completely amateur fashion with three different size screws, a hand cut gasket, and some sealing compound. One of the screw heads, probably a Philips head in a previous life, was striped initially. This plate now leaks and introduces diesel fumes into the aft stateroom. Yet another repair project awaits me.
It was good to hear from all of you. Your replies have enabled me to put some of my J/42 problems in perspective. Thank you.
J/42, hull no. 74, 2006