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Old 03-05-2013, 05:00   #1
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Need Help with Plumbing Re-Design

Replaced all of my plumbing on my now 34 year old boat. When my freshwater tank empties, it takes quite a while after filling the tank, for the pump to suction prime. Currently, i have no check valves in the system. The pump is physically located not more than 1 foot higher than the the top of the tank. Its a shurflo with ballz, 3 gpm if memory serves. Not a very complex plumbing system, one hot water heater and the fresh water runs to the galleys sink and head sink/shower. I am adding a stern shower this week, cold only. What improvements can I make to protect my system and pump?
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Old 03-05-2013, 05:29   #2
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Re: Need help with plumbing re-design

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Originally Posted by Stirfryd View Post
Replaced all of my plumbing on my now 34 year old boat. When my freshwater tank empties, it takes quite a while after filling the tank, for the pump to suction prime. Currently, i have no check valves in the system. The pump is physically located not more than 1 foot higher than the the top of the tank. Its a shurflo with ballz, 3 gpm if memory serves. Not a very complex plumbing system, one hot water heater and the fresh water runs to the galleys sink and head sink/shower. I am adding a stern shower this week, cold only. What improvements can I make to protect my system and pump?
The West Marine catalog has a diagram of a typical boat potable water system. I suggest studying it. There should be a check valve in the water heater. It's often built in to one of the connectors.

As for taking quite a while for the pump to prime, there could be a very small leak between the tank and the pump that allows it to suck air along with the water. Otherwise, the simplest way to avoid this problem is to refill the tank before it runs dry.

Since you're going to all the trouble, why not run both hot and cold water to the stern shower? My wife and I use the cockpit (stern) shower if we are anchored with no one around. It saves cleaning the other one.
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Old 03-05-2013, 18:49   #3
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Re: Need help with plumbing re-design

Do you have a Whale (or other) manual pump at your sink? If so, and the check valve goes bad, it will suck air from there and create havoc.
I recently figured this out after having my sinks start sputtering a lot of air except when my tank was COMPLETELY full. Thinking I had a corroded uptake pipe in the tank, I pulled the tank cover off (36 nuts), just to find the uptake intact. THAT was when I noticed a T off my hose going from the tank to some dark space under the floor. Once I traced it out and found it went to the manual pump at the sink, I just put my finger over the opening while running the fresh water pump and viola! no sputtering water.
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Old 03-05-2013, 19:24   #4
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Re: Need help with plumbing re-design

I have to use the foot pump a little to get the ShurFlow re-primed after running a tank dry. My pump is below the water level. But the water must siphon out of the tank. Sometimes I blow on the vent line ... if the tank is full ... same result. I assume the pump is a bit tired (8 years?) and doesn't move air well.
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Old 13-05-2013, 23:05   #5
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Re: Need help with plumbing re-design

I'll be looking at my entire plumbing (not much) system soon. I have no idea how it works, just that it does, which does me no good in the event something happens. Since its a new (to me) boat, I gotta figure out what goes where and how this does that....lots of valves and stuff, so I gotta figure it all out. This may be a wet and gross mission.
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Old 14-05-2013, 04:30   #6
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Re: Need help with plumbing re-design

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I'll be looking at my entire plumbing (not much) system soon. I have no idea how it works, just that it does, which does me no good in the event something happens. Since its a new (to me) boat, I gotta figure out what goes where and how this does that....lots of valves and stuff, so I gotta figure it all out. This may be a wet and gross mission.
I had several friends in the plumbing shop when I was working and they summed plumbing up like this:

Hot on the left, Cold on the right, and **** won't go uphill!

The West Marine catalog contains a diagram of a typical boat's plumbing system. Take a look at it for starters. Find your pump now while it still runs and makes noise.
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Old 14-05-2013, 05:40   #7
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Re: Need help with plumbing re-design

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There should be a check valve in the water heater. It's often built in to one of the connectors.
why , not common here, whats the purpose of such a check valve.

Dave
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Old 14-05-2013, 06:35   #8
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Re: Need help with plumbing re-design

I installed a Tee fitting in the water distribution line (immediately after the pump), with a ball valve in the Tee.
Open the valve to relieve air (purging to eliminate any air trapped in the pump ), and let water flow out (into the bilge), until you get full (airless) water flow, then close valve and continue purging to the furthest fixture.


A check valve, located at the cold supply inlet to the water heater (with the directional arrow pointing towards the tank), prevents hot water from backflowing into the cold water system. This usually isn’t an issue, unless the cold water line tees off to another fixture very close to the water heater.
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Old 14-05-2013, 06:57   #9
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Re: Need help with plumbing re-design

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A check valve, located at the cold supply inlet to the water heater (with the directional arrow pointing towards the tank), prevents hot water from backflowing into the cold water system.
Yep, that's the reason. Remember, as the water heats it expands. Without the check valve, it goes back into the water tank.

For the catalog impaired, here is West Marine's basic water system diagram:



In this case, the check valve shown prevents the city water from going backwards through the pump and overflowing the fresh water tank. As I posted above there will usually be a check valve built in to the water heater inlet fitting. You won't see it unless you remove the fitting and look through it.
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Old 14-05-2013, 08:09   #10
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Re: Need help with plumbing re-design

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A check valve, located at the cold supply inlet to the water heater (with the directional arrow pointing towards the tank), prevents hot water from backflowing into the cold water system. This usually isn’t an issue, unless the cold water line tees off to another fixture very close to the water heater.
Huh, the water system is pressurised , how could that happen!

It just Ive never seen these valves here in such a situation, nor have I ever fitted them like so!

dave
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Old 14-05-2013, 08:14   #11
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Re: Need help with plumbing re-design

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Huh, the water system is pressurised , how could that happen!

It just Ive never seen these valves here in such a situation, nor have I ever fitted them like so!

dave
Examine the inlet fitting on the water heater. It's built in to the fitting, that's why you've never seen one.
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Old 14-05-2013, 08:22   #12
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Re: Need help with plumbing re-design

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Examine the inlet fitting on the water heater. It's built in to the fitting, that's why you've never seen one.
Nope , not on the Isotemp ones Ive installed, mixing valve yes, check valve no. Ive plumbed two houses and three boats, cant see the point of one!

Dave
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Old 14-05-2013, 09:02   #13
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Re: Need help with plumbing re-design

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Water Heaters


MARINE WATER HEATERS
A marine water heater is the electrical or propane powered appliance that is used in the boating industry for space and hot water heating where the shower, washing-up and personal hygiene are the main applications. A marine water heater is a small, insulated tank downstream of the pump. There must be a pressurized water system so that the marine heater can operate. The pump draws water from the storage tank and fills the water heater tank. Inside the marine water heater there is an electrical heating element and usually a coiled tube called a heat exchanger. When AC power is available, the electrical element, which is controlled by a thermostat, heats the water. Away from the dock, the hot engine coolant is routed through the coiled tube to heat the water in the tank when the engine is running. A marine water heater system generally consists of the tank, water heater unit, pump and hoses. Valves and filters provide safer use and some systems include an accumulator that reduces pump cycling. The heater consists of an electrical heating element and a coiled tube called a heat exchanger.
A marine water heater has four threaded ports. The tank inlet connects via a tee-connector to the outlet hose from the pump. It is important to have a check valve in this line or in the heater to prevent hot water from migrating back toward the pump. The outlet connection supplies heated water to the hot side of all faucets, also using tee-connectors. The other two ports are for the heat exchanger connection, which varies depending on engine installation. It is a good idea to use only metal fittings to plumb a water heater. Many professionals don’t recommend using plastic. If a pressure-release valve isn't integral, the heater will have a fifth port for this essential component.
A marine water heater can heat water quickly and it can also deliver every possible ounce of usable hot water from the tank. A marine heater sometimes is made of a zinc allow heating element that is designed to withstand accidental operation on an empty tank. Some marine water heater use double tube construction, preventing any possibility of engine coolant contaminating the fresh water system. .........................
(emphasis added)

http://www.jmsonline.net/marine-plumbing/water-heaters.htm
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Old 14-05-2013, 09:16   #14
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Re: Need help with plumbing re-design

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It is important to have a check valve in this line or in the heater to prevent hot water from migrating back toward the pump.
received wisdom is all well, but Ive never seen it happen and its not common here, so much for received wisdom, thats all.

I regard that piece from JMS as akin to dont put your cat in the microwave

http://www.surejust.co.uk/PDF/connections.pdf

Heres a good quality clarifier manufacturer, to comply with modern standards the cold is actually partially fed into the hot side. No check valves to be seen. I just don't see the point of them .

dave
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Old 14-05-2013, 09:27   #15
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Re: Need help with plumbing re-design

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received wisdom is all well, but Ive never seen it happen and its not common here, so much for received wisdom, thats all.

I regard that piece from JMS as akin to dont put your cat in the microwave

http://www.surejust.co.uk/PDF/connections.pdf

Heres a good quality clarifier manufacturer, to comply with modern standards the cold is actually partially fed into the hot side. No check valves to be seen. I just don't see the point of them .

dave
There was one on my previous boat, built into the inlet adapter. I've personally seen and felt it. I would expect to find one in my current boat's water heater but I haven't had a reason to take it apart.

That said, it's not worth my time to argue the point any further. You have seen what you have seen and I have seen what I have seen. We can go our separate ways believing what we believe.
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