Tech Wiki

Smelly Head Solutions

Why does it stink?

I have an odor problem and can't figure out what it is. The boat is a 1987 Catalina 34 with an anti-siphon setup in the overboard discharge hose, and that is spliced into the primary vent line for the holding tank, which vents through a stanchion base. An odor problem started last summer, early in the cruising season. I replaced all of the hoses on the holding tank -- and flushed and flushed the system. I still some odor. I smelled the bilge -- whew! I cleaned the bilge several times with a lot of different products. The ultimate solution was to put a gallon of chlorine bleach in the bilge and let it sit for a day. That got rid of the odor. Unfortunately, the bilge constantly has water in it -- leakage through the mast? I can't find any other source. In a few weeks, the odor returned. I got religion and thoroughly flushed the holding tank out again and started using K.O. holding tank treatment. That seems to work well. This episode was near the end of the cruising season. For winter lay-up, I filled and pumped the holding tank four times, then added antifreeze. I also added the toilet bowl chlorine tablets to the bilge to keep any bacterial growth down. The smell is back. There is water in the bilge, but the smell is no stronger there than in the boat in general. I'm not sure the smell is coming from the holding tank, but I'm not sure the smell isn't coming from the holding tank. I seem to recognize the smell as more like rotting plywood, but maybe I'm deluding myself. However, I can't seem to find any soft wood or localize the source of the smell. Any advice would be gratefully appreciated. I've run out of things to check. Pete Smullen

Some solutions from the C34 Mailing List

  • I had a similar problem and decided to convert my starboard water tank to Head Use Only. This solved the problem of smell from dying plankton and other things in the sea water. The fresh water head works much better and now no chance of overflow or sinking the boat. If you are concerned about hose or tank leaking drop a color dye pill in the head and flush into the holding tank. Watch the bilge for dye. As to water in the bilge: Check your packing gland. This should drip on drop every 15-20 seconds. I installed a dripless-teflon coated packing and no more drip or water. I also installed a one way valve in the auto bilge line. I still get some water from the mast, window and station bedding leaks. Did the funny rotting plywood smell you described smell like vinegar? If so, this may be the same smell you get when popping hull blisters. If so check it out ASAP. I was advised buy a surveyor to keep the bilge dry and the keel bolts dry as if they are continually covered with water it starves the stainless steel for oxygen and deterioration of the stainless steel threads can result. R. Norquist

  • Start by back flushing the vent line from the stanchion to the holding tank and see if there is a leak. Also check the plastic "T" for the macerator pump, mine cracked once. If you think you may have a leak place food dye in the tank and fill it with water, you should be able to find the leak. If the "T" is cracked you will find it when you pump the tank out. When putting the food dye in the tank place some of it in the toilet bowl and pump it into the holding tank. By doing this you can check for a leak going into the holding tank (Rich, Rebellious #328).

  • I had the same problem with Juliana, and didn't figure out the answer for more than a year. The problem turned out to be leakage from the female plastic housings that are epoxied into the side of the holding tank. They had been leaking slightly *underneath* the hose nipple, where you can't see, resulting in the accumulation of sludge -- yes, sludge -- under the tank itself. What a mess! I ordered a new tank from Catalina (only $70), tore the old one out, and replaced the couplings. No problem since. Also, I installed a SeaLand charcoal head filter (available from West Marine) on the vent line -- this prevents odors from reaching the cockpit when somebody pumps the head while you're underway. Bryan Pfaffenberger, Juliana #680

Fresh Water Head and Overflow Control

I got a little tired of the Head Overflowing when someone forgot to leave the handle down. I decided to convert the smaller starboard Fresh Water Tank to a dedicated fresh water supply for the head. The starboard water tank is about the same size as the holding tank. This is great because you reduce the risk of overfilling the waste tank. I added a 1/2" Tee off the inlet sea cock and put a 1/2" ball valve and a one way check valve on the fresh water inlet side of the Tee. Then disconnected the stabbed fresh water tank from the fresh water supply system and ran a direct line from the water tank to the Tee. Then connected to the head inlet line to the other side of the Tee. End result and benefits:

  1. I don't need to use the inlet sea cock. It stays shut. I only need to open the ball valve to the fresh water tank.
  2. The head never overflows. The top of the head is is just a little higher than the top of the water tank.
  3. The head odor disappeared or at least is better. You don't have all those sea water microbes dying and causing additional odor.
  4. We only use the large stern water tank for drinkable water. We use it more and this keep things fresher.

R. Norquist

Vent Filter

I just finished building a vent filter for the holding tank. The breakthrough thought came from my wife, while we were discussing the possibilities, and I asked what the filter medium could be. She immediately suggested activated charcoal, which makes perfect sense, and I was soon off to Hechingers for parts. I built a U-tube structure with 2" PVC sanitary piping and 3/4" elbow end fittings to connect into the vent tubing where it rises up past the electrical panel in the aft-most cuddy on the port side. The U is about 12" long, and 8" wide, and is filled with a mixture of straight activated charcoal and something called "Ammocarb". These came from a pet store, where they are sold in bulk to people who own fish. They are used to filter out the same noxious gases in fish tanks. I have never seen the commercial product, and didn't know how big the absorber bed is, so I figured that a bed that was 2" in diameter by about 30" long should be fine. If not, I can extend it by adding some more loops. The U also has a side tap so that I can empty and refill it when the charcoal is exhausted. The whole thing cost about $20 in parts,and about $10 for the charcoal. And I can re-fill it very cheaply. I filled one leg with Ammocarb, and the other with straight charcoal. It works very well, and we now don't have to worry about stinking up a whole raft of boats any more! Ralph Caruso

More information on this subject:

More information on this subject can be found from the “Head Mistress,” aka Peggy Hall,” the expert on marine heads and holding tank systems. Her book is available at most marine stores or online. She moderates a forum at select forum, then expert forum, Marine Sanitation. Here is the link: She has several articles including successful flushing, odor cause and cure, intake water odors, maintenance and more.