For all of you about to retrofit a holding tank to comply with regulations, or wish to upgrade from a less efficient system, or installing a system on a new boat, how would like to have a system that is self-cleaning, self-emptying, does not need "Y" valves, eliminates the need for a vented loop, eliminates the need for a macerator pump, is easily cleaned and flushed and is reliable? The KISS system allows you to install or retrofit the best possible working system without complicated plumbing, electrical connections and drilling a minimum number of holes in the boat.

The concept is simplicity itself. The tank, installed above the waterline, is emptied overboard by gravity. All waste goes through the tank. The toilet pumps directly to the top of the tank. (MSD) there is no "Y" valve or any other extra leak-prone joint in the system. The toilet itself can be either manual or electric, it makes no difference. The outlet at the bottom of the tank leads to a "Tee." One of the fittings goes to the seacock, the other to the deck pump-out fitting. To use the tank, you close the seacock. To flush straight through, you open the seacock. No Complicated pumps or valves, no smelly leaky vented loops, yards less of piping, dozens less hose clamps and no electrical connections necessary.

The K.I.S.S. system is elementary. The toilet pumps the waste up above the waterline into the holding tank. Gravity pulls it out. Simply by closing the outlet seacock, the holding tank is in use. If your are emptying it offshore, you just open the seacock and it drains out by itself. To rinse, just pump the head.

Another important aspect to this system is that the tank is higher than most, especially those way down in the bilge, thus reducing the amount of "head" (suction) needed to pump the tank from dockside pump-out facilities. By reducing the vacuum, the tank and hoses will last considerably longer and be less prone to operational failure.

1. Since the toilet discharge will be anti-siphon protected, it can be located anywhere, either above or below the waterline. However, to mount below the waterline, you must have a positive shut-off for incoming water. Not all commercial toilets are so equipped thus the possibility of requiring an anti-siphon valve in the inlet line*

2. The tank must be secured above the waterline. In the case of a monohull sailboat, figure the top of the tank must be safely above the heeled waterline, the bottom must be above the upright waterline. The bridgedeck of a multihull makes an ideal location for a tank. Most catamarans and many trimarans have space in lockers in the foredeck area that are above the waterline that normally are not easily accessible but are close to the boat centerline.

3. It is important to place the deck clean-out line "Tee" as close to the outlet seacock as possible. This will leave the least amount of waste not pumped from your deck pump-out facility. It is imperative to use high quality hose that will not collapse under suction. The very best product for this job is regular schedule 40 PVC pipe. Use a minimum of short hose lengths where there is the possibility of twisting or wracking from hull movement. Remember, hundreds of thousands of RV units are plumbed this way, dump by gravity and have little or no vibration failures.

4. With any holding tank system it is vital to keep the vent pipe clear. If the vent pipe is not clear, it is possible to build up pressure in the tank and either rupture the tank or blow the hoses off. In either event, a great unpleasantness will ensue. Therefore, do not use the cheap clear vinyl tubing. Use a high grade, thick wall, reinforced tubing. All tubing should be opaque. Letting sunlight get into the lines allows the algae to grow that causes a most unpleasant odor.

Have the vent so located that you can blast the wash hose down it occasionally to keep it clean. Bigger is better. Most successful installation use 1 1/4" vents. Fresh air must get into the tank as well as fumes getting out. Several catamaran manufacturers have the vent under the boat between the hulls. Install the vent pipe free of severe bends. Many installations require two vent pipes.

The very best tanks will be polypropylene and have a hemispherical bottom. The drain hole will be in the center, thus making it close to impossible to leave any residue in the tank.

The next best, will be a polypropylene tank with the drain on the bottom and the most likely candidate will be a tank picked at an RV store that has the outlet at the lower edge of one side. In any event, it is necessary to have the inlet in the very top.

The tank inlet from the toilet must be at the very top. The waste must free-fall to the bottom of the tank, leaving the top open to continue its secondary function as a vacuum break .

Free surface water is consideration. A low, flat tank, with a lot of surface area, can create a wave problem in a partially filled tank. If you purchase from marine sources, they may provide you with baffled tanks when you get to that large a size. If you use tall skinny cylindrical tanks, standing on end, you need not worry about free surface water and will have the most satisfactory shape. Even standing a rectangular tank on end will make a difference. It is important to be creative in your choice of tank and location. A tank standing on end could be installed in a large chain locker or hanging locker, perhaps directly above the outlet seacock.

Gauging the size of your tank.

The holding tank should be sized by how you expect to use it. If you are going to spend the better part of your cruising at marinas, and you will be most often be getting pumped out from your deck fitting, install the largest practical tank. If you are going to spend most of your time in waters where you will be mostly pumping straight through, a small tank will suffice. Small is about ten to fifteen gallons, large is 25 gallons and above. Rubber tanks will also work, but they are much harder to clean and flush and more likely to smell. If you figure a minimum required capacity of one half-gallon per day per person, you will be close to your requirements for size.

If you have a deck wash pump and hose, flushing through the vent is possible and practical. Just open the seacock, stick the hose in the vent pipe and fire away.

Simple is beautiful. The KISS MSD system cuts the cost of installation in more than half by eliminating the most expensive parts. It makes operation virtually foolproof. No fancy instructions, no puzzling over which way the "Y" valve is turned, no more short-circuited rusty old macerator pumps. Elimination of the vented loop, a source of odor and malfunction, is axiomatic. The free-flow of air from the vent to the tank and the open hose in the tank at a height considerably above the waterline subsume its function.

Parts in a conventional system: (per MSD)

tank

Macerator-pump

2 "Y" valves

1 Electrical switch and wiring for macerator pump

1 vented loop

1 outlet seacock (some configurations require TWO outlet seacocks, another big hole in your hull!)

1 inlet seacock

1 "Tee" fitting (or two, depending upon configuration)

hose clamps on estimated 22 joints double clamped where feasible

hose clamps for vent double clamped

Vent fitting

deck pump-out fitting

Yards of hose or PVC pipe.

1 tank

1 outlet seacock

1 inlet seacock

1 "Tee" fitting

hose clamps on minimum number of joints, double clamped where feasible

hose clamps for vent double clamped where feasible

Vent fitting

Feet of hose or PVC pipe

*The use of fresh water for flushing may modify that requirement.

1. If you have a watermaker or spend considerable time at marinas where you can obtain water easily, plumb your system to flush with fresh water. You can have a switch over to sea water if you like, as a standby. Using potable water as flush water will eliminate most of the maintenance problems associated with marine toilets.

2. Make sure your tank is empty when you leave the boat for an extended time period. In hot weather, the material may dry up and cake, causing serious blockage problems. The more complex the system, the worse the problems. On systems that isolate the holding tank from the rest of the system with "Y" valves, this can be especially bad because of the tendency to neglect the tank anyway.

In cold weather, there is the possibility of freezing and rupturing both tank and hose. Many an owner has come back to spring commissioning only to find a split hose or fitting due to the nature of his installation.

3. There are certain marine jurisdictions that do not allow any connections for overboard flushing, even if they are sealed and locked. The KISS system is the simplest to convert. Just remove the "T" from the system and replace it with a sweep elbow. You then have a classic pump out only system. (Many cruisers use that most simple system and pump out with a hand operated diaphragm pump from the same deck fitting when it is convenient for the to do so)

4. Always rinse thoroughly while you are being pumped out at pump-out station.