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Old 10-18-2017, 10:37 PM   #1
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Check valve on fresh water tank

Vessel is 33 yrs old, fresh water system is original, twin SS 150gal tanks with SS 1/2" pipes & both port & starboard gate valves are frozen. The port tank feeds slowly. Although never used by me, the vessel does has a shore pressure water connection.

Last weekend, to correct the slow feed & frozen valves, I removed all plumbing from the port tank pipe to the boost pump. Between the SS tank pipe & gate valve was a brass check valve. Restriction was debris stuck in iron nipple into check valve. I rebuilt the new port system with brass nipples, brass ball valve, pex tubing & sharkbite fittings. System works wonderfully. Now to rebuild the much more difficult (due to limited access) starboard system & tie both together.

Should I add a new check valve to each leg of the new system?

My initial concern is if connected to pressure water it could back feed into water tanks causing them to overflow.

Thx, PD
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Old 10-19-2017, 01:06 AM   #2
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I'd be inclined to disconnect the connection to shore pressure. Just fill your tanks and let your pump supply water from your huge tanks.

It used to be common for boats to hook into shore water but not so much these days. There is some danger of shore water sinking your boat if something in the system fails while you're not there. Besides which, you want to change the water in your tanks fairly frequently.

The shore pressure water should T into the system down stream of the pump. The valves in the pump should prevent water from getting back to the tanks. If water gets back past the pump, it will just come out the tank vent which probably just lets it go overboard.
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Old 10-19-2017, 04:18 AM   #3
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I fitted 2 SS tanks, Port and Starboard to a previous boat and I put a SS lever type shut off valve at each tank (make sure you can reach it, or fit an extension so you can) and a 1'' pipe as an equalizer/cross balance pipe. On that I fitted a 'T' from Port and Starboard to feed the water pump. I only used high quality food grade 316 SS fittings and food grade pipework. The system still works perfectly for the new owner.
I fully support Parks comment to ditch the shore connection and turn over the water in your tanks regularly.
When re-filling I dissolve 2 tablespoons per 200 gallons of Bi-Carbonate of Soda in boiling water, stir until completely dissolved and add to the water tank when refilling, a cheap and cost effective sterilization of your water system, it's harmless and tasteless.
Before refilling water tanks, take a clear glass, fill it from the tap and let it settle, smell it, taste it an hold it up to the light for impurities.
I forgot to do it once DUH ! it was a PIA to clear and clean the system afterwards.
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Old 10-19-2017, 05:57 AM   #4
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Not sure why you have check valves at the tanks, you just need one between the shore side water and its entry into the "system".

That is if you have a standard marine water pump that acts as the check valve between the system under pressure and the water tanks

Some people put one at the feed to the pump but it is usually redundant.
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Old 10-19-2017, 06:08 AM   #5
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The most common use for a check valve is in the hot water tank feed .

This is so expanding water as it heats does not feed back into the cold supply.

An accumulator is needed for this to work.
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Old 10-19-2017, 08:20 AM   #6
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The reason for check valves between pumps and tanks is that it prevents losing prime when the pump turns off. A coarse screen filter keeps crud at bay. If your pump is below the bottom of the water tank outlet, then not an issue.
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Old 10-19-2017, 08:53 AM   #7
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HeyJude, I noticed a similar problem on our Manatee when we first took ownership. The boat had been a dock queen using the shore pressure reducer bulkhead fitting in the cockpit. I could only get water supply to the fw pump from the port tank and figured out the starboard check valve was fouled in the closed position. I found the piping system was all copper tubing and bronze check valves and ball valve tank shut off valves, I guess KK stopped using gate valves by the time they got to building our boat hull #69. As you mentioned the tank shut off valves are hard to get to, as Irish Rambler mentioned, I installed reach rods on the ball valve handles. By closing the port tank supply and opening the stbd I finally got the check valve to open and feed water to the fw pump. I have for years used the fw pump with both tank supply valves open and removed the dock water pressure reducing valve as Parks mentioned as a safety change. I always have a new fw pump spare in case of failure, changing the pump out takes minutes. The 300 gallon capacity of both tanks last a good while and drawing water from both tanks keeps the boat in trim and the tanks fresh and ready for cruising.
Your question about keeping the check valves, I would as I believe there function is to keep the tanks from back filling from dock pressure water supply. Worse case scenario, you can’t use the fw pump and have to use dock pressure for various reasons would be one reason to keep the check valves in place. The other is Kadey Krogen did a really good job designing the Manatee systems so I defer to there expertise.
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Old 10-19-2017, 10:14 AM   #8
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As others say, check valves not necessary. In the event you choose to use dock water directly, your tank shutoff valves can be used if the pump itself does not prevent back flow. I too agree with avoiding using dock water.
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Old 10-19-2017, 10:24 AM   #9
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The fw pump is comprised of two check valves with a pumping chamber in between. No need for any more check valves.

Second others to not leave dock water tied into the system. Can sink the boat and often pressure is way high. Just fill and use the tanks. Keeps them more fresh anyway.
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Old 10-19-2017, 11:56 AM   #10
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Quote:
The fw pump is comprised of two check valves with a pumping chamber in between.
Not necessarily, and not on any of the FW pumps I am familiar with, not to say I am familiar with them all. On my old Hatteras, and other boats I've seen, a check valve is right at the tank to prevent loss of prime. Always best to check the specs and manual.

When we were at a dock for extended periods, we always used shore water when we were on board, and turned it off when we left, at least most of the time. We had a well maintained plumbing system, and while it was nice psychologically to have it off when away, I really had no more need to than I have on any of my homes. Between the pressure reducers and various valves, even a catstrophe would be handled by the bilge pump system. I verified this via the onboard fresh water tap when cleaning bilges. By the way, that's one way of gauging how adequate your total bilge pumping system is.
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Old 10-19-2017, 01:57 PM   #11
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"The fw pump is comprised of two check valves with a pumping chamber in between.
Not necessarily, and not on any of the FW pumps I am familiar with,..."

George, if you disassemble the FW pump on your boat now, you'll see two one way valves. These are the valves that Ski is talking about. The pump wouldn't work without them.
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Old 10-19-2017, 06:55 PM   #12
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Neither the GalleyMaid DC pump or the Flojet (Sears Craftsman rebranded) shallow well pump on my boat had two. Nor the Shurflo washdown pump.
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Old 10-19-2017, 08:23 PM   #13
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The GalleyMaid and the Sears would have had exterior check valves or the pressurized water would have flowed back through them to the tank and the pump would cycle on and off. In the case of these pumps the check valve could have been between the tank and the pump. You are correct in that these pumps require only one check valve, not two.

All of the ShurFlo Wash Down pumps I'm familiar with are swash plate diaphragm pumps with internal valves.
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Old 10-19-2017, 11:26 PM   #14
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Thanks all

HopCar...thx for your system knowledge & advise...I'll continue NOT using shore water supply. I've seen a boat nearly sink because of broken shore water system.

Irish Rambler...I'll note your advice for sanitizing water of unknown quality. The new ball valves have a 3rd port with a secondary ball valve that allows system to be drained if necessary. https://www.zoro.com/webstone-brass-...12/i/G5273931/


psneed...roger, our Jabsco boost pump operates as you speak & holds pressure between uses.

FF...roger

caltexflanc...roger, I'll observe operation at minimum tank level to see if pump loses prime. If so, I can add check valves to new system.

HiDHo...HeyJude was plumbed same & starboard valve all but inaccessible due to generator. My starboard tank plan is to find a skinny plumber & have him carefully remove the frozen starboard valve & copper tubing. With that gone, install the necessary fittings to run pex to a new port ball valve 3" from the "T" to the boost pump. That will put both port & starboard valves with 12" of each other & very accessible. I also carry a spare boost pump with male/female quick connects. If we need to use shore water we'll drag water hose thur galley window with a spray nozzle. Another mod is I ran 1/2" clear tubing from the bottom sight tube connections thru the bilge into the engine compartment & up the bulkhead so we can see the tank water levels by lifting the most forward of the 3 engine access panels. For 6 yr we never knew quite how much water we had aboard because the old sight tubes were crazed. We timed our water fills & the boat was almost always out of trim because the port tank barely passed water.

sunchaser...roger

Ski...roger
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Old 10-20-2017, 07:54 AM   #15
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Yep, well type pumps and Galleymaids don't have internal checks as part of the pumping process. My statement was a little broad, covers any type of diaphragm pump.
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Old 10-20-2017, 08:11 AM   #16
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Thanks All.
I assume my check valve, after the T on top of the tanks is there to not let water flow back from the pump, as the pump is higher than the tanks.
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