Grey Water Tank/Discharge System…

…is IN!

So I thought I had this all buttoned up until my wife said “What about the deck pumpout?” …uh …dohb! A couple weeks later, its done, including the deck pumpout.

The Tank

Recall from this previous post that we added a sixteen gallon polypropylene tank under the center fuel tank as there was room, and, well, we want to utilize as much space as possible, even if it makes things more complicated! Well, the tank is now finally installed, with the added necessary accessories, and it may never be removed again. Recent modifications include adapting the pvc elbow discharge  fitting to accept a diptube to help the pump remove as much stuff as possible. Also added as a standard WEMA sending unit for monitoring the tank level. The tank is blocked up about an inch on the “far end” so the contents, by gravity, will pool on the opposite end near the diptube to help ensure most of the contents will get pumped out (this assumes the boat will ultimately sit on her lines of course).

Inspection port, Dip tube, Tank Level Sender

End of tank (left), plumbing to pump and side deck.

The Pump

The waste dicharge pump is an ITT/Jabsco waste pump model 50890 (24volt version). It is a diaphragm type pump with one-way joker valves in the inlet and outlet. The diaphragm pumps like a bellows to pull waste from one end, and out the other. We have the previous version of this pump on the small boat, and let me say, Jabsco has made some nice improvements with the new model. First, it is more compact and can fit in smaller spaces. Second, you can rotate the diaphragm mechanism on two axes, relative to the motor. This allows the pump to “customized” to fit even tighter spaces.

This is a very nice pump. But, after experience with the previous pump on the small boat, let me say that having access for future servicing is CRITICAL. I don’t know how many times I have cursed this pumps predecessor. The most common issue is a cracked or torn joker valve. Once that happens, the valve(s) wont close, preventing the pump from priming or pulling the waste up from the tank. We have had this happen before on an extended cruise. Replacing the valves is easy, but the last thing you want to do is tear out half your hanging locker to get to the pump (which is where it is installed on the small boat). So, in this installation, care has been taken for an easy access location, which is, under the floor board in the “tunnel” between the main salon and the aft cabin.


Discharge pump, in compartment under floorboard

The updated version of this pump makes it even easier (I dont think we could have installed the old model here. It would be too big.). The pump is mounted on the sidewall of the floor support. It uses hex bolts and  tee-nuts on the opposite side to make pump removal a snap needing only one wrench (of course).

The Plumbing

The hose to/from the tank snakes through a couple holes in the bulkhead, up to and behind the (future) cabinetry in the galley, under the side deck. Now, I am not sure I mentioned this before, but we are “allowing” for the possibility of an automatic dishwasher and/or washer/dryer (stop laughing). The cabinets are large enough to hold these appliances. These features are not high in the priority list, but we are planning for them just in case. So, part of the plumbing includes the “standpipe” that these two appliances would ultimately drain into. Right next to the standpipe is the vented loop for overboard discharge and the Y-valve to direct the discharge line to the deckfill for pumpout, or overboard to the thru-hull.

Cramped plumbing under side deck.

The plumbing input to the tank has a Tee to accommodate future items like the galley sink discharge. It will also have an easy access pipe to allow a plumbers snake to be used to clear out any clogging that may happen.

3 comments for “Grey Water Tank/Discharge System…

  1. January 17, 2011 at 4:42 pm

    Looks great. I have a particular hatred for that Jabsco Y valve when used on a heads system but it should be fine for grey water (valve kept blocking, handle sheared off).

  2. January 17, 2011 at 5:31 pm

    We haven't had a problem with that Y-valve on the small boat (so far, knock-on-finely-varnished-teak). I noticed my dealer sells replacement handles, so maybe that is not an uncommon experience? Truth is there are limited Y-valve choices. This installation would not be possible without the nice swiveled ports on this jabsco Y-valve.

  3. January 20, 2011 at 11:41 pm

    I think it is a good thing your wife checks up on you.

    It sounds like something I would do or not do. LOL

    Bill Kelleher

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