Thursday, January 29, 2015

Dry Bilge

Mike and Rebecca on s/v One Love really want a dry bilge.  And air conditioning a boat in the tropics was working against that goal.  I am also an advocate of the incremental test/installation process that Mike used.  Here's what he did:
Remember my post about wanting to have a dry bilge? Well, we ultimately decided to go the route of installing a couple of sump boxes to deal with the air-conditioners’ condensation. We selected this one and Michael brought two of them with him when he arrived on the 15th.

I am 80% of the way through installing the first of the two. Here are the steps I have taken thus far:
  1. Before getting started, we dried and cleaned the bilges.
  2. I then ran a line from the AC unit’s drip tray outlet down into the bilge to see if it would gravity feed the water where I wanted it to. I put a short length of hose into a plastic container. We ran the air conditioner and it fed the water as I had hoped. I was surprised at how quickly it filled the container!

  3. Before doing any actual plumbing and electrical connections, I wanted to test the unit to ensure that it worked, and also to ensure that it would pump the water high enough to exit where I planned to dispose of it. We tested this by taking the sump box out into the cockpit, connecting a hose to the outlet and filling the box with water. While Rebecca held the hose in the air, I applied temporary power to the pump using a 12V plug and alligator clips. It worked as we had hoped.
  4. The next step was to attach the inlet and outlet hoses. We had already made one trip to the chandlery to purchase parts for this (hose, clamps, fittings). This particular box has multiple inlets of various sizes. The strange thing (to me) is that you need to saw off the end of the inlet that you want to use! It seems to me there could be a better solution but it is what it is, I cut it off.

  5. I temporarily positioned the box in the bilge, a location which is at a lower level than the AC unit. This allows the condensation water to gravity feed into the box, as tested earlier. I connected the sump pump’s power leads to a bus bar in a nearby junction box which supplies 12V to the electric bilge pumps. The outlet hose I simply ran into a nearby sink. We tested the operation of the unit in this configuration and it worked perfectly. The AC unit ran for some time and the bilge remained dry as we had hoped.

The next step is to permanently connect the outlet hose. My plan is to T it into the sink drain hose. In order to do that properly, I’ll need to place a non-return valve (check valve) in the outlet hose, just before the T. This will prevent any water draining out of the sink from finding its way into the sump box’s outlet hose*. Unfortunately, the chandlery will not have the check valve I need until some time tomorrow. Until then, we’ll be living with a hose zip tied to our sink.

*Alternatively, I guess I could route the sump box outlet hose so that it feeds down into the drain hose. Gravity should then prevent the sink water from making its way into that hose.

Notes: I also want to plumb our refrigerator’s drain into this sump box. The sump box that I’ll be installing on the starboard side will have to deal with the condensation from both the salon AC unit, and the starboard hull’s AC unit.
[Tho not clean enough to drink, the condensate from the air conditioner would be an ideal source of ion-free water for battery maintenance. -Ed]

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