We have a gray water tank and had so much trouble with everything about it. It took us years to come up with a solution that only needs simple
maintenance once every 6 months (and believe me, that is very good!).
We have one central gray water tank, which is in the keel-sump. All gray water drains in there by gravity, like in a house, and that part is fantastic. This also means you only have one pump, one set of
wiring, one floatswitch, one breaker/fuse etc. I would advise to do this if possible. Build a tank in the
bilge with some
plywood, glass and
epoxy. We have a perspex lid with rubber
gasket. We mounted a standard Beckson
inspection lid in the perspex lid for quick access during
maintenance. Choose the size so that your fist will pass it.
Now is where the trouble starts: pump, float-switch, discharge and pickup hoses, strainers etc. Macerating pumps are worthless as they quickly seize with hair around the shaft/knife/impeller. A big step forward was the Whale Gulper 220 pump. Get it and you solve half the headache. This pump will pass anything that can pass it's inlet.
But the float-switch is bad too. The previous owner started with a Waterwitch electronic switch which failed to trigger often as fatty residue covered it (that is soap residue!). He changed to one of those very expensive switches with a float inside a tube and that was what we got with the
boat. I hated that so much because the float would quickly seize inside the tube and all the holes would clog etc. When the switch fails, you are in trouble because the tank will overflow. Not just through the drain in the heads but also through the lid because the
gasket is never perfect after some period of use. We decided that this will not do and started experiments. I will skip all the failures and come straight to our solution:
Pick-up pipe: Buy a 3/4" PVC adapter from pipe to thread. Cut a hole in the lid that just fits this adapter and use
sanding and JB weld to fit it into the lid, with threads facing up. Now put the lid on the tank and measure the distance to the bottom of the tank through the adapter (to the top of the adapter). Cut a piece of 3/4" PVC pipe (schedule 40) to that size and fit it to the adapter with PVC cement. It will be too long. Keep cutting off small pieces until it is about 1 cm (1/2") above the bottom of the tank. That's it, no strainers, just $1.- worth of PVC. Now mount a 90 degree PVC
elbow thread to hose-barbs on the adapter using Permatex no. 1 as thread
sealant. This part is never going to wear out and will never clog.
Float switch. Use the cheapest
Rule switch you can get: the type with that hinged plastic float. Buy 3 of these (add 2 to your spares). The trick is to mount this switch at the bottom of the pick-up pipe. We made a mini-bracket out of King Starboard and attached that to the pipe with hoseclamps. We actually used monel wire with our spiff Clamptight tool but hoseclamps will do. You probably have to cut some slits in the bracket to pass the hoseclamp through, this is why you need a Dremel or (and) Rotozip tool aboard.
Drill a little hole for the wire through the lid, pull the wire through and fasten it to the pipe with plastic wire ties. Mount a small terminal-block on top of the lid, put the expensive heat-shrinked terminals on the two wires and connect them to the terminals. Put a little dot of silicone where the wire comes through the lid (both sides). Done.
Discharge pipe: we already had a 1.5" hose coming to the tank so we fit a 1.5" PVC coupler (female thread to female thread) in the lid just like for the pickup tube. We mounted a 90 degree PVC
elbow (thread to barbs) on top to accept the incoming 1.5" hose. We mounted a straight 1.5" thread-to-barbs fitting on the underside of the lid plus a piece of hose. That piece of hose will not be straight, it will have a bend from being rolled up. Use that to your advantage and mount it so that anything entering the tank falls on top of the float-switch. I know that Nigel Calder writes to keep the float switch as far away from pick-up tube and discharge hose as possible. I also know I had a lot of failures before finding this solution... believe me, this is what works. The float-switch is auto-cleaned and everything will
work great.
There's one more thing to this: if you ever need to take the lid off, you have that 1.5" hose attached to it's top making your life miserable. You can't put the lid aside. We
solved this with a very smart coupling from Good Turns. It has right-hand-side thread on one end and left-hand-thread on the other. You turn it one way and it couples the hose, the other way and they come apart without using knifes, heat-guns, dremel etc. We had to hunt on-line stores to find one but it's worth it.
80% of trouble
solved, 19% to go: you need to find a solenoid equipped with a timer. We used one off an old
Raritan electric head (it times how long it flushes after pressing the flush-switch). I see it in the catalogs so it's there. Mount that solenoid between float-switch and pump so that the pump will continue pumping after the float-switch switches off again. This timer can be set using a mini screwdriver. This trick only works with the Whale Gulper pump because it can pump water-air mixture or even just air (like manual bilgepump, it's the same thing). Start filling the tank until float switch activates. As the pump evacuates the water, it will start drawing air but still pump liquid too. At this point, it will pump nasty stuff that floats in the tank. Adjust the timer so that the pump stops when it is only pumping air (clear hoses help a lot here). The gulping sounds go neatly with the Gulper pump and they also let you know all is okay in there.
1% trouble left.... can't get rid of it but this is what we do for maintenance: once every 6 months we open the Beckson-lid, shine a light in and yell Bah! Hose it down, close the lid and done. 5 minutes.
After two years the float-switch failed. Replaced in 30 minutes incl. changing mounting holes because
Rule decided to upgrade and change the switch. That's why you need to buy 3 the exact same ones ;-)
We have this setup for over 4 years now and no more trouble. I think the upgraded float-switch is better because it still works but that might also be because I now have the exact same ones as spares lined up.
cheers,
Nick.
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