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Old 20-03-2009, 05:11   #1
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Lavac install tips

Planning to install a Lavac popular head. Any tips on install. Boat is a Corsair 31.


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Old 20-03-2009, 06:44   #2
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When doing my install I replaced all the sanitary hose on the boat so it was a fairly involved project. I installed 2 Y-vales so the pump for the Lavac can also be used to pump the holding tank overboard when offshore.

On the vent of the vented loop for the intake seawater I connected a 1/4 inch tube that runs to the bulkhead replacing the flapper valve. When pumping the Lavac you hold your finger over the tube to get suction. When you take your finger off the suction is broken. A very positive way to prevent continued siphoning and for the next person to be able to use the Lavac immediately.

I also found that ring that holds the gasket in the lid of the toilet was not properly sealed with the lid. This caused a chronic problem of not getting a good seal with lots of air being pumped overboard. I solved that by removing the ring and roughing up the surfaces and using waterproof glue to permanently seal the ring to the lid. No problems since.

We are happy with the Lavac.

John & Cheryl Mallon
Sceptre 41
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Old 20-03-2009, 08:24   #3
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My Lavac empties into a custom ply/epoxy holding tank, mounted as high up under the foredeck as possible, allowing for the curve of the hose entering the top. At the base of the holding tank, I have installed a tee in the exhaust line, with the additional hose leading to a deck pumpout fitting. The direct waste drain then goes to a large plastic ball valve, turns 90 degrees into the thruhull fitting (located just ABOVE the waterline). With the waste valve closed (and LOCKED, per USCG), the unit is perfectly acceptable by the authorities. In open ocean areas, simply open the ball valve for instant, GRAVITY-FED, not electrically macerated and pumped, discharge.

The vent lines on the tank reveal the secret, though. Instead of the usual single 1/2 inch hose found on most holding tanks, mine has two vent lines, each 1 1/2 inches in diameter, which lead to opposite sides of the bow, near deck level. This is to allow strong cross drafting of air through the top of the holding tank. The reason for all of this? Aerobic digestion of the waste in the tank, supported by bacteria from K.O., a product sold at West Marine, and other sites. My boat is the only one on the dock that doesn't have a smelly head. The odors are generated by anerobic (live in the absence of oxygen) bacteria, as well as the formaldehyde and perfumes added by conventional head chemicals. The stuff works and is the perfect complement to the Lavac installation.

When underway, there is no need to lug along a hundred pounds of toilet waste. If you are in open waters and feel the need to have a personal waste discharge, the Lavac pumps the poop up and into the tank, where it flows downward and out the throughhull. A couple more pumps and the lines and tank are rinsed relatively clean. Later, with a fresh batch of K.O. and some seawater, the bugs are gobbling up any available waste in the lines or tank, turning them into environmentally safe building blocks for other forms of marine life. This is actually how septic tanks work on land, and allow human waste to enter the earth safely, even when one is pumping drinking water a hundred yards away.

The best parts, though, beside the good vibes and no nasty smells, are that things work without costly maintenance, they work flawlessly, and don't cost you very much at all. And it weighs very little, in the bargain.

Pictures: Pump up -gravity out holding tanks
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Old 20-03-2009, 15:22   #4
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Hanging low, pumping high...

I did a Kiss installation of my LAVAC with a holding tank.

My big mistake was to make the holding tank tall and narrow and to install it just under the deck. This makes it hard to pump and allows what can be a considerable amount of backflow.

If I was to do it again I would use a short holding tank with the bottom just above the water line.

For ventilation I used two 1/2" hoses at opposite corners of the tank, one going to the cabin top and one to the cabin side. I hoped to always get some slight pressure differential.

The best trick that I have found for managing smells is to put a little vinegar in the bowl and to pump it up so that it is sitting in the pump. This keeps "calcate" build up down and the pump clean so there is reduced backflow.

If a large capacity is needed I would use a second tank, possibly fed using an electric pump.
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