Adding a 12V Fresh Water Pump

I do have a secondary low voltage pump on my 72' Hatteras. It's nice to have the backup, but I rarely use it.

I don't have a picture and it would probably look fairly convoluted if I took one. Here's my best description of the layout though.

Freshwater line to T. T out to either pump. Valve on the front and backside of both pumps. (I wouldn't think this necessary, but it is a nice feature if you have to change out the pump or have a problem.) Water line out of each pump to T in outgoing side.

One pump is basically in line with the additional one off to the side. You will want a self priming pump I your tank isn't above the pump location. My pumps are controlled via a breaker panel (1 ac, 1 dc) and I just turn off whichever one I'm not using. When I switch over, it's 4 valves and 2 switches and away we go.

It looks like you will have a fairly easy install based on the photos. Good luck. Hopefully I was helpful. Please feel free to let me know if you need some more help and I'll do what I can.

Trig

Here's a setup I did with a Stingray 240VAC pump primary and a Jabsco Dual-Max 12VDC as backup (it's kind of lost behind the hose). Both pumps have their own seperate inlets so only the outlets needed to be valved, breaker panels right above them and the water tank is integral beneath the shelf they're mounted on.

You are correct in that most pumps have check valves on their outlets. The reason we add an external valve (usually a ball type) is to be able to remove and repair/replace the faulty pump without disrupting service on board while those repairs are carried out. This may not be important for day trips but much more so when travelling. We always add couplings too so you don't run into problems unscrewing pipe fittings.

Bill has it exactly right. Depending on whether you do your own repairs and maintenance, it would behoove you to add the valves and unions for uninterrupted water service should you have a breakdown.

If you are only cruising short distances in areas where there are many service providers and suppliers available, it may not be as big an issue. I know from my experience (and it sounds like Bill's) it has been nice to have to have running water for a shower when the pump broke down in the evening or during a transit.

If the pump just stops working that would be the case but many times they fail a little more spectacularly and you find a fountain in your engine room spraying things that really don't need a bath. Troubleshooting and repairing is a lot easier on the dock in most cases so the expense of a couple ball valves and unions will pay dividends in the future.

And yes Triggerfish, sometimes owners and guests get a little testy when they can't get their shower when they want to or the toilets don't flush on demand. Wrapping up at the end of a long day is bad enough, working on a broken pump in a hot engine room (till the AC units cool it down of course ) doesn't make for a happy crew.

i have the AC well pump and the DC pump.

I really like the set up and the double systems.

they both work at the same time if on and there doesnt seem to be any issues.

I only use the 12V pump when anchored out as the AC pump uses alot of juice to start up and would drain the batterys and mostlikely trip the inverter

Mmwhit

Mine is quite straight forward from the factory. T off the elbow intake to the 110, T into the house supply, 12 volt Pump in between. Check valve as you think necessary. If everything is tight it's just freshwater going back and forth on the changeover. My 12 volt pressure stinks. But I run my genny from 8 to 10 if I'm not on shore power. I like a hot shower and firm ice for that evening cocktail

If you have to ask the question, maybe you're not skilled enough to do the job. It's a really easy thing to do.

If you have to ask the question, maybe you're not skilled enough to do the job. It's a really easy thing to do. Don't forget to run the proper size wiring and proper breaker. I would also tidy up that rats nest of wires with some cable ties.

Mwwhit

I don't have any pictures of mine. Different set up anyway. But I have a 3/4" (?) elbow tapped directly into a 2' (?) supply side elbow leading to my 110V pump. That 3/4' hose runs to the supply side of the 12v pump mounted near by. Then a 3/4 inch line leads out from the pressure side of the 12v pump and T's into the water system after the 110V pump. This setup effectively isolates the 110v pump and pressure tank by going around it. Hope that's helpful.