Essential information on tank maintenance

Q: What causes the rotten egg smell in the heads compartment?

A: Hydrogen sulphide gas produced by decaying algae and bacteria left in the toilet raw water inlet pipe. The only way to solve this problem is to fit a fresh water flushing kit which introduces fresh water into the pipe before leaving the vessel.

Q: I have put diesel in my water tank, is there anything I can do?

A: There are companies who will come to the boat, remove the contents of the tank and clean the tank. They can also clean a fuel tank that has water put in it. Try Express Lube who can be found at

Q: Can I join two water or fuel tanks together?

A: To join two tanks together a “balance pipe” is required. This should be at least 1″ in diameter on each tank and situated as low as possible.

Q: Does my tank need a separate vent fitting?

A: Yes if it is a rigid tank made from either stainless, aluminium or polyethylene. The air has to get into the tank when emptied and out of the tank when filled. Remember the deck filler is sealed with an O ring to prevent sea water or rain water getting in. A flexible tank does not need a breather because it will collapse when emptied and expand when filled.

Q: What size vent do I need on my waste holding tank?

A: 1 ½” vent is the industry standard in the UK or a series of smaller vents that achieve the same cross sectional area. Smaller tanks can get away with a 1″ vent but it is not advisable to go smaller as they are prone to blocking if the tank is overfilled.

Q: Can an inspection hatch go on the side of my tank?

A: Yes it can if it is bolted on with a suitable gasket. Most off the shelf hatches are not suitable as they are really only splash proof. The tank manufacturer should be able to advise.