One freshwater deck fill or two?

AaronD

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Aug 10, 2014
770
Classic Yachts 26 Newberg, OR / Shelton, WA
One of the main projects this winter is to plumb water tanks + pump to a sink faucet.

Boat: Classic Yachts 26. Usually moored in the summer and trailered home off-season. I'm new to marine plumbing - even just having a sink and drain this summer was a move up in the world from just water bottles on our C-22. :cool:

No practical space for a solid tank. Old flexible tank under the aft berth, which I plan to replace with a new tank of ~15 gal; and adding a ~25 gal tank under the starboard settee - we'll mostly use the aft tank, and keep the midship tank for backup and to level out some of our list to port (the galley, head and 2 of our 4 propulsion batteries are on port, so some water on starboard will help).

From some old threads, including this discussion, the clear consensus is to include a manifold / switch and draw from one tank at a time, which was definitely my plan.

But with 2 tanks (or the 5 that sail sfbay noted!) would one prefer separate deck inlets for each tank, or a single deck inlet and a manifold / selector valve to select which tank to fill? Reasoning? I have one deck fill currently, and it should be straightforward to add another - and that was my leaning, but I could be argued toward a fill-side manifold instead.

FWIW - we'll probably be using a low-flow faucet (osmosis-style). Ideally, I might do a foot-pump to conserve water, but I plan on an electric instead, so I don't have to pump for an hour to empty the tanks before trailering (we need to shift weight forward on the ramp, and definitely when towing). Maybe eventually I'll do both (foot-pump for daily use and electric to drain tanks).
 
May 1, 2011
5,538
Pearson 37 Lusby MD
But with 2 tanks (or the 5 that sail sfbay noted!) would one prefer separate deck inlets for each tank, or a single deck inlet and a manifold / selector valve to select which tank to fill?
I have three water tanks on my boat. Each has a separate deck fill.
 
Feb 26, 2004
23,493
Catalina 34 224 Maple Bay, BC, Canada
I have two tanks with two separate fills. I never use one of the fills. Why? Because one tank easily drains into the other tank because it is higher. This works thru the manifold.
Of course, each of your tanks needs its own vent.
 
Jan 11, 2014
14,171
Sabre 362 113 Fair Haven, NY
Keeping the tanks isolated is important so 2 fills are best. If there is one fill and it becomes contaminated, there is no way to fill either tank. The fill can become contaminated with mold and mildew or by a faulty gasket.
 

AaronD

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Aug 10, 2014
770
Classic Yachts 26 Newberg, OR / Shelton, WA
Keeping the tanks isolated is important so 2 fills are best. If there is one fill and it becomes contaminated, there is no way to fill either tank. The fill can become contaminated with mold and mildew or by a faulty gasket.
Good point.

And the input seems consistent. Survey says... Two deck fills.

Thanks, all.
 
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Sep 24, 2018
4,690
Catalina 30 MKIII Chicago
My boat has two fills. We only use one tank due to some mildew in one of them (one of 1000 projects). the 20ish gallons last a few weeks. I empty my tanks at the end of the season using the faucet and electric pump. No need for a separate drain pump as the water will just go down the sink drain
 
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jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
24,758
CAL 35 Cruiser #21 moored EVERETT WA
The size and number of tanks is dependent on the volume of water you need for the coastal cruising you are planning. Recommendations vary based on activity, here is one source.

Things You'll Need Water For
  • Drinking: 0.5 - 0.9 gallons (or 2 - 3.5 liters) per day
  • Showers - 0 - 17 gallons (65 liters) per day
  • Laundry - 0 - 40 gallons (150 liters) per load
  • Cooking - 0 - 1.8 gallons (7 liters) per day
  • Interior/exterior cleaning - 0 - 26 gallons (100 liters)
  • Backup - 0 - infinity
One size does not fit all. If you plan 2 tanks, then two inlets can help reduce the plumbing of two tanks. It also may help to isolate tankage should something contaminate one tank.