millhaven_nice_guy wrote:
Or go to your local Home Depot or Lowes and buy some PEX fittings so you could tee in a drain line with a valve you could just drain into the bilge. The system is put together with reuseable fittings so modifications are very easy. This way you would save battery power and let the water out when you pull your plug.
If it's the same as other models then it's using the Whale brand 15mm tubing fittings. I would not mix that with generic residential plumbing fittings. Too much added risk for leaks and hassles. If you want a drain then just get a Whale 'tee' fitting, a valve and a length of the 15mm tubing. Cut an existing line somewhere, put in the tee then run the tubing to somewhere convenient to place the shut off valve. Like from the tank over to an accessible place for the valve. Then run the rest of the tubing to a convenient draining point, like the bilge. Just make sure to use zip ties or the u-shaped clip mounts to secure the tubing so it's not flapping around.
Be aware that if you drain it in this manner you may also want to open the filler port to allow air into the tank. The opening on the vent is pretty small. Opening the filler would let it drain a bit faster.
But I don't know that I'd bother. If you're filling the tank from a good source and using some tank treatment tablets there's not much chance of it going bad. Sure, it might get that funky plastic tank flavor but that's about it. If I were worried about it I'd probably just open a tap and let it run until empty. Just make sure not to let the pump run dry.