It should also be no less than 24 inches away from any opening into an accommodation space. If fitting is to be located in hull topsides, select a protected spot where it will not be subject to damage from pilings, etc. Form a gooseneck in the vent line above the vent fitting to prevent seawater from back flooding to the tank. This also may keep the vent line from kinking. Bed fitting to avoid water leakage into interior of boat.
Vent line filters Install per manufacture's recommendations.
Siphon breaks A vented loop in the discharge line can allow foul odors into the boat. Run a small hose from the siphon break vent fitting to the holding tank vent line or to a separate vent fitting located above the maximum heeled waterline. Diaphragm pumps should be mounted above the level of the top of the holding tank so that they will not be sewage filled when the tank is full. This will minimize permeation of the flexible diaphragm material. If pump is not installed above the tank level, service valves should be provided to enable pump removal without releasing tank contents.