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Old 10-29-2015, 12:11 PM   #21
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I replaced the gate valves on my fuel shutoffs with bronze ball valves. I still have a couple of gate valves on my freshwater and RW washdown systems that I believe are fine for their purpose. One is at the freshwater washdown spigot. Another is at the aft RW washdown spigot. The third is at the water heater drain. It came installed on the water heater.

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Old 10-29-2015, 12:28 PM   #22
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Originally Posted by tallswede View Post
I have only one gate valve on my boat. It is on the engine coolant to the water heater coil. I use it to restrict flow through the heater coil. I feel this is not too severe a service for this valve due to the antifreeze solution in the cooling system. Other through hulls etc. should all be ball valves for quick reliable operation.

Gate valves aren't typically used for throttling as the gate is wedge shaped and when in the partially open the flow past will rattle the gate in the seats. On cheap small diameter valves (and big expensive ones too), this will often lead to the gate to stem connection wearing and the gate liberating itself from the stem. If the stem is in the vertical position, the gate drops and shuts off flow.

In your case, not a big deal. But a good reason not to use them "improperly" in a critical service.

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Old 10-29-2015, 01:12 PM   #23
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Originally Posted by FF View Post
The hassle with gate valves is the stem is usually made of "free machining" brass.

The brass de zincifys and you loose controll of the valve....
On an old gasser we had, the raw water control was a gate valve. All of a sudden one day we lost cooling. I went to shut the gate valve thinking I had clogged the raw water screen. The valve kept turning in my hand until I realized the stem had separated from the gate and it dropped into the closed position. I had to remove the gate to get back to the dock for a haul out the next day to install a proper ball valve.
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Old 10-29-2015, 02:50 PM   #24
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Yep they will do that or if throttled way down actually cut a groove through the gate or body of the valve. One advantage of a gate valve, especially on a pressure system is that it reduces water hammer in that it opens slower. Once again different valves for different purposes.

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