Typically the water pumps are rubber diaphragm style with either one, two, or three diaphragms. There are often inlet and outlet check values as well. The checks and diaphragms are rubber flappers that push/pull, seat/unseat alternately as a drive motor runs. As the rubber gets old and as gunk grows in the water system the rubber shrinks, hardens, and deforms so that it no longer seats properly to push/pull water or prevent back flow. One of the first symptoms is that the pump has difficulty drawing water (dry priming). Since air is less viscous than water, it leaks past the sealing surfaces. If the pump is already primed then the more viscous water will create enough back pressure to seal the seating surfaces. You can then pull water from the tanks. As long as a relatively uninterrupted supply of water is maintained the pump will continue to work. Once the tank goes dry there is no more water to seal the seating surfaces and swapping to the other tank may not be enough since the pump is no longer creating a suction to prime the pump.
Propylene glycol and bleach, the 2 chemicals typically added to freshwater tanks, will degrade rubber components over time. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Mon, Jul 9, 2018, 9:09 AM Maurice Poulin via CnC-List < cnc-list@cnc-list.com> wrote: > Hello, > > As new owners of our C&C 30 mkii, we were out for a first weekend and had > a ball. Very comfortable and loads of fun on the water was our overall > appraisal! But we did run into a bit of a snag and I turn to the board for > assistance hopefully. > > The boat has two tanks and we ran out of water on the forward tank pretty > much on our last evening so switched over to the second tank but never > could get the pump to prime and draw water from the second tank and charge > up the lines. Checked all connections and no leaks, plenty of water in the > settee tank, checked strainer on the pump all okay. Both tank connect to > this distribution gizmo with assorted ball valves that connects to the pump > and from there to the galley and head. As the boat is new to me, I suspect > I may not be working this gizmo thing correctly, not opening up the correct > valves or maybe closing them while thinking I am opening them. I see on the > valve handles that one side is pointed while the other side is round, > possibly indicating on and off? Anyways, confusion and the fear of running > down the batteries to troubleshoot stopped me from tearing this thing > apart! I figured I would ask questions before doing exploratory work at the > dock! What should I be doing appropriately to switch from tanks or can you > run both tanks together, or not? > > Alternately, the pump seemed to be not priming but I thought it was a self > priming pump perhaps I am mistaken in that, so how do you prime a pump > would be an alternate question? > > Thank you all from this newbie that had a hand pump at the galley > previously! > > Cheers, > > Maurice Poulin > C&C 30 MKII, Monoloy > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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