What is a grey water tank system and why have it?

a. We have a grey water tank located in the bilge, adjacent to the galley sinks. It is custom made of fibreglass, like the head holding tanks. The capacity is about 14 gallons. By using a grey water tank we avoid having three thru-hull seacocks and three valves for grey water discharge. Items feeding to the tank are: 1. the galley sink(s), 2. the fwd head sink and shower sump, 3. the aft head sink; [The sinks drain by gravity and the shower sump is pumped.] The tank is hand discharged by its own diaphragm pump (Whale Gusher 8 – discontinued) through a seacock above the water line; it is emptied daily. The tank has a vent and a cleanout hatch. Here is the wooden mold, Grey Water Tank Mould.Here is the Grey Water Tank (fiberglassed) and the Grey Water Tank Installation. My grey water discharge is protected against ingress by the flap check valve in the Gusher diaphragm pump. David S., s/v #050, Opportunity

b. [Lester Note: I destroyed an 8 mm movie camera and damaged an expensive Plath sextant when I had a grounding in my Bristol 29 sailboat in Manasquan Inlet, NJ in 1978.The boat lay over on its port side while seawater rushed in via a sink. I had to call the Coast Guard to pump out the boat; I was too dazed to realize what was happening because I was exhausted from too little sleep during my nine day ordeal returning from Bermuda singlehanded. Moral of story: Close sink seacocks before grounding or better, install a grey water system.]

c. Endorphin is equipped with a grey water tank (sump) which receives grey water from the 2 showers and head sinks onboard. It is located high in the aft area of the main salon’s bilge. The galley sinks drain directly overboard. A bilge pump drains the sump with a manual switch. There is an inline screen filter. Our whole system is less than ideal. The sump is not water tight. When full the sump over flows into the bilge. All in all, at this time, our grey water system does not provide much in the way of an example for other boat owners. Thank you, David H. (#195, Endorphin).

d. The builder, Swift custom boats, put a tank center of bilge, with a float, and a macerator pump under a seat. All galley, sinks, and shower drains to it. Float kicks on pump when full out to a thru hull at water line. Works great! Cappy D. (#169, CapBam)

e. Yes, #023, Simmerdim is equipped with a grey water tank. The 4 gallon tank is located under the salon floor, center, a meter in front of the mast post. A 12 volt pump discharges the contents via the head sink thruhull. There is a screen filter between the tank and the pump to prevent clogging. The filter needs to be cleaned once a month. The tank drains the galley sink, the ice box, and the shower. So far, our main usage is with the galley sink and the 4 gallons is not large enough in a liveaboard situation. It fills quickly and requires being pumped too often, once every two days. Our galley sink is double so it is my plan to divert one of the sinks directly to a thruhull so we can choose direct discharge or tank discharge. An access is needed to clean the tank at the end of the season; otherwise you can get bad odours. Gilles L. (#023, Simmerdim).

f. I have one because at one time it was suggested that the Ontario government would make them mandatory. Basically, the system collects the grey water from the sinks and the shower and pumps it directly overboard or via the holding tank. Charles L. (#115, Melodia).

g. May 22, 2011, Boat got launched, the usual plumbing issues, seals and gaskets dry up over winter ……other than that all OK ! Enclosing a photo of my Grey Water Tank…..Frank B., s/v (#186, Visitant).

h. I don’t have a grey water tank on my personal boat but I dealt with them on larger yachts that I operated for other owners. Grey waters are all the drains from sinks, showers, washing machines (clothes or dish). It accumulates in a tank so that you can dump it out at a pump out station or offshore. Some boats only had the shower and sinks and drained the washing machines directly overboard. Although there was no law where I sailed to have them, it just seemed a good idea not to send overboard grey water when you swim around the boat. In most cases it did not mean much. I think that a 40′ boat is too small to have a grey water tank unless it is mandatory in the area you sail (like Lake Champlain in Vermont). I think that most important is consider using soap that has no phosphate and that is biodegradable, deal with any cooking oil separately and put the solids in the garbage. Avoid using chemicals that will have a negative impact on the environment. This is also true for the black water tank. People put tons of chemicals in their toilet to cut down the smell. The smell has to do with the installation of the toilet and tank. Chemicals don’t help much just like the lady who went to the doctor because she had gasses. The doctor gave her a small spray can with wild pine odor that she was to use in emergencies. She found herself in an elevator with a young man and decided to try the system. After a minute she asked the young man if he smelled anything. After sniffing and thinking about it for a second or two, the young man said:” Yes it smells like someone sh….. under a Christmas tree” I have been in many boats that reminded me of that story All plastic hoses will eventually transpire the contents that circulates through them, hence the smell. We used PVC (household) piping throughout with flexible joints. If the tank itself is plastic, you glue aluminum foil on all its surface to prevent the smell from going through. That is the way my boat is now and I have no need for pine scent. Have a wonderful day. Marius Corbin