How "powerful" are the fynspray type hand pumps?

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How "powerful" are the fynspray type hand pumps?

Postby rick_bradshaw » Sun Nov 18, 2007 9:57 pm

I've been plumbing in a fresh water filtration system. There are a few issues but the filter does the job we "hired" it to do. The "issues" have to do with the fynspray type hand pumps.

First, I rebuilt both of them. The salt water pump works well. No issues with that at all.

Second, fresh water hand pump doesn't seem to have the "oomph" to pull the water through the system. True, it doesn't just go from tank to pump anymore. The units didn't work at all when we bought the boat.

The system is designed to go 1) from tank to pump without going through the filter ("normal" operation), 2) from tank through filter to pump, and 3) from tank to filter to pump using the ship's fresh water pump to "push" the water through the filter to the hand pump. In doing this, I extended the hose a bit so that there is room to install ball valves in the system to isolate the different methods to retrieve water.

I think the lack of power in the direct to pump (#1) mode may be due to extending the hose and not having it going straight to the pump by the shortest route possible. I can rectify that by changing the routing. No problem with that. Does that sound like the problem or is there something else that seems to be an issue that I haven't found yet?

In #2 mode I can see air bubbles being pumped through the hoses but little in the way of water. I think the hand pump just doesn't have the "power" to draw the fresh water through the filter. Is there any kind of "work around" that has been found for this? We'd like to be able to filter our drinking water without expending electrical power to do so.

In #3 mode the ship's fresh water pump overwhelms the hand pump and puts the water through without pumping. The handle stays "down" in place. "Adjusting" the ball valves in the system will adjust the stream and the force of the stream. Since this isn't easy to do, it isn't quite the solution. Among things I'm considering is finding a very low power consumption/low pressure pump and putting that inline to push through the filter only and with its own switch at the galley sink area. I don't have time to do that right now so it may be a future "fix" that I will need to get parts for and take with us. Any other suggestions/ideas?

One thing that I have noticed is that the handle on the fresh water pump seems to have pressure on it. The handle will raise and the piston go down. There is enough pressure so that it feels like it "kicks" up a bit when it is manually pumped. Not a good feeling. This is sometimes true whether it is pressurized or not but is prevalent after pressurizing the system suggesting that it is holding pressure but in reverse of how the unit works when running the ship's fresh water pump. The salt water pump does not have this pressure issue. They were both rebuilt in the same way using identical parts. I'm concerned about damaging the pump in some way. Since I have to remove the pump from the counter top by removing it from under the counter and disconnecting the hoses, rebuilding or repairing isn't looked at too lightly. Any ideas about this issue?

TIA.
Rick

s/v La Vita
1987 HC 33T #136
http://la-vita.us/blog/
rick_bradshaw
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Location: Currently cruising pacific Mexico

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