Diagnosing a freshwater pump issue

Hi All,

I am looking for help diagnosing an issue with my freshwater (potable) water pump.

The pump is a ShurFlo and I believe the manufacture date is 1998. When I bought my boat, the pump would come on and then cycle a handful of times after use, but eventually turn itself off (while remaining powered on). Gradually the cycling became worse.

Symptom 1: Pump runs continuously
The pump will not turn off now, even with the water faucet off, and all of the manifold valves closed.

Symptom 2: Water flowing to bilge from stern.
While the pump is on, wate flows into the bilge from the stern of the boat. My boat has two tanks aft of the bilge where I see water appearing - my hot water tank and a freshwater tank beneath my starboard cockpit locker.

Fix attempt 1: Removed the pump, cleaned some junk from a pre-pump screen filter on the output side.

Fix attempt 2: After reading about problems with the check valve, I disassembled the pump, removed the diaphragm at the bottom, cleaned it and reassembled. The pump moves water like a champ when the faucet is open and it is drawing water from a full tank.

Fix attempt 3. Disassembled the hot water tank. An audible gasp of a vacuum being opened occurred when I unscrewed the freshwater connectors from the hot water tank. It does not seem like this tank is leaking.

Fix attemp 4: Access and inspect the freshwater tank at the stern. I have not done this step and it will involve removing my blackwater tank (oooh gross) which is why I am writing this forum thread to make sure I am not missing something obvious.

What I don't understand is how I can keep pushing freshwater into my bilge if all of the valves on the manifold are closed. (That is what happens). Is this a sign of the check valve in the pump being bad? If am not serving any water to the input side of the pump, it seems like I must be forcing pressure into the post-pump side of the plumbing and I have a leak somewhere.

Any ideas, oh ye wise and clever fellow boat owners?

I already had one broken Ronco freshwater tank I replaced. I am confident no one has removed the starboard aft freshwater tank during the life of the boat (I was pulling factory bung plugs during my assessment.

Do you have a Whale foot pump in the fresh water system? The plastic casing on mine developed a hairline crack and was squirting water out whenever the fresh water system is under pressure.

Had a similar problem two years ago. Pump wouldn't shut off and bilge was full of water. Hot water tank was rusted out.

Probably It wont; turn off because there's air in the system. Many causes for that.

On the face of it, if when pump is running and pumps water into the bilge, there's a leak. However in my world such a logic chain is often misleading. (and currently is, since Thelonious has fresh water in her bilge and I don't know why). And I cant find a leak of any kind.

I don't know what the audible gasp signifies. Pulling water through a water heater--should that create a "vacuum?" Should it create any air pressure differential of any kind? Maybe somebody else will say, of course it can.

This is mostly a sympathetic response rather than a helpful one, because I spent two hours last weekend troubleshooting why my pump wouldn;d turn off. I looked for air leaks in all the impossible spaces, threw my back out doing it, got stuck under the cockpit, scratched my arms raw, and have been limping like Quasimodo ever since.

Then I pumped the fresh water foot pump three times. I already knew it admitted air, but of course forgot that I already know it. Problem solved. I guess the fresh water in my bilge is rain. Even though it hasn't rained.

If water is indeed being pumped from stern tanks to the bilge by the Shurflow, then you will have to identify the water path using the usual means of flour barrier, salt dam, toilet paper laid in the speculated path and so on.

It seems to me however that it would be a substantial breach of the plumbing to make the pump not turn off (a drip wouldn't do it)). Whereas a very minor air intake from a cracked fitting means the pump runs continually.

If you have an accumulator, check that. They have an internal membrane that breaks.

Lots of words, not much help. Fresh water plumbing issues on a boat requires a long duration of thought and theory. But find the leak, or prove to self that it is fictional.

Hi,
An unlikely cause, but given that you are stumped, I'll post it for your consideration,and it's easy to check.
I also have a Shurflo pump, which began to act up. I phoned their tech dept. (very friendly and helpful) and learned there is an adjustment screw on the bottom, under a label (why there??). This tiny Allen screw increases or decreases the pressure at which the pump comes on and cycles. My pump had worked fine, but gradually began to cycle on/off within seconds, which was clearly a problem.
I adjusted the Allen screw a 3/4 turn like the tech suggested, reinstalled it, and water sprayed out the bottom of the pump. When I adjusted the Allen screw in the other direction, the water spray stopped, and the pump has worked fine since--I must have initially turned it in the wrong direction.
I know you cleaned the pump, but you may want to watch it briefly while it's running to see if it's spraying or leaking like mine did when I adjusted it wrong. If so, find that Allen screw, adjust, and fix.
Frank
ps. This fix could also solve the problem of a pump running continuously or cycling too frequently, even without a water leak.

jtsai said:

Do you have a Whale foot pump in the fresh water system? The plastic casing on mine developed a hairline crack and was squirting water out whenever the fresh water system is under pressure.

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I do have the foot pump. I hadn't even considered this could be the problem. Thank you.

JSM said:

Had a similar problem two years ago. Pump wouldn't shut off and bilge was full of water. Hot water tank was rusted out.

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Good idea. Removing the hot water tank entirely and testing is on my list (though it was air-tight when I removed the first freshwater connector).

goldenstate said:

Good idea. Removing the hot water tank entirely and testing is on my list (though it was air-tight when I removed the first freshwater connector).

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Word of caution about that hot water heater. Years ago my hot water heater had a crack in it that I think wasn’t big enough to cause the fresh water pump to recycle on and off but big enough to slowly leak into the area where the 120 volt wires were connected. This problem, which was probably happening over years , resulted in increased resistance and one day a small electrical fire. I was fortunate enough to be nearby to catch sight of the smoke coming out of the stern vents on my E32-3. It was very scary. Replaced the heater but found massive amount of corrosion at the 120 volt connections so please do check that while you’re running down you leak.

My water pump sometimes runs for a long time when all valves are closed which I can solve by simply opening a faucet to let air out of the system which sometimes happens when I switch tanks. I don’t have an accumulator tank but it’s on my list of things to install.

Bolo said:

Word of caution about that hot water heater. Years ago my hot water heater had a crack in it that I think wasn’t big enough to cause the fresh water pump to recycle on and off but big enough to slowly leak into the area where the 120 volt wires were connected. This problem, which was probably happening over years , resulted in increased resistance and one day a small electrical fire. I was fortunate enough to be nearby to catch sight of the smoke coming out of the stern vents on my E32-3. It was very scary. Replaced the heater but found massive amount of corrosion at the 120 volt connections so please do check that while you’re running down you leak.

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Thanks. The 120v heating element in my tank has never functioned so I have ignored it. I will review when I pull the tank.

Bolo said:

My water pump sometimes runs for a long time when all valves are closed which I can solve by simply opening a faucet to let air out of the system which sometimes happens when I switch tanks. I don’t have an accumulator tank but it’s on my list of things to install.

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This was my standard operating procedure (let the air burp out of the system by opening a faucet) but it no longer does the trick and the pump continues to run. Good idea though.

Unrequested comment from up in the balcony:
I did solve the problem of the pump cycling when small amounts of water were needed (like at 3 am) by installing an accumulator. That was over 15 years ago. Still works OK, but sometimes our pump check valve misbehaves and it cycles occasionally anyway.
If addressing this now, I would probably just replace the whole pump with a newer pump version with the variable pressure scheme. I understand that they are near silent in operation. It's probably just me, but it's the noise rather than the operation of the pump that is irritating.

Don't overthink this, the possibilities are few:

1. System leak after the pump, clearly indicated in symptom #2 in the opening post. It's leaking, you just have to find it.
2. Deteriorated check valve inside the pump.
3. Loss of prime to the pump.
4. Any combination of the three. Don't be fixated on finding a single magic bullet. The entire water system is old, perhaps at least 24 years old as suggested in the opening post.

More disassembly work.

I removed the hot water tank and decided it should be replaced anyway. Some rusty water came out of my head faucet during testing, and with an entire plumbing system built out of plastic tube, the pipes in the water heater are I think the most likely culprit. Hopefully I can make the electric heating element in the new one work (the old one did not). Here's what it looks like disassembled, minus insulation:



Also took out the holding tank and had the chance to bring it home and clean it out. (Pumped out first, of course, at the marina dock.) By repeated partial-fill, sloshing, dumping down the city sewer, I was able to get to clear water without any calcified chunks. I could tell with my sloshing I broke loose a good amount of calcified material.

The tank is a Ronco B175:



Oh but wait, I'm supposed to be fixing my freshwater pump cycling problem. Beneath the apparent floorboard of my locker is my third freshwater tank, a Ronco B194.



The 1.5 hours of time invested unscrewing all of the stuff to get to the tank yielded no useful information. At least, it was not more readily apparent where my leak was.

I unscrewed the output side of the pump and held my thumb over the outlet after turning on the system. With the system capped off this way, the pump stopped, as the system is designed. (I.E. Parrothead's #1 problem diagnosis above.)

I can hear some sloshing of water between my engine bay and the pump in my galley sink cabinet while the pump cycles. My current working theory is that the hose line that sends pressurized cold water up into the hot water heater has failed in the best of all places, which is hidden inaccessibly in the TAFG. It is probably zip tied to the underside of the grid, making the pull-through of a replacement line impossible.

Next steps are to try to identify which of three quest hose lines in the invisible vicinity is the culprit and then replace it.

Oh, and replace the water heater and put the holding tank back.

My water heater replacement, Raritan to Kuuma, is here.

Christian Williams said:

My water heater replacement, Raritan to Kuuma, is here.

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Has the Kuuma performed adequately? I was on my way to buy one at West Marine.

Minor victory at sea today.

My supposition that the Quest tubing was ziptie-screwed into the underside of the TAFG was correct. I drilled an extremely BF hole in just the right spot between my engine bay and the galley sink. BF stands for "Below Floorboard" What did you think I meant? (I'm here all week. Be sure to tip your waitress...)

Please note that I was able to remove these floorboards in 5 minutes only because I have had them up before. It took approximately 1.5 hours the first time to break the silicone sealant factory bond. I will never ever ever glue sole board back to my boat. So much easier to access with screws alone.



My placement of the hole saw was so excellent that I cut apart one of the three hoses in the process. But fortune smiled on me and the hose in question was the same one that was already leaking. I had purchased a hole cutter sufficiently large that I could stick my hand through and found not one but two zip tie locations that I subsequently severed with a pair of diagonal pliers.

After cutting the zip ties, I liberated the under-grid section of tubing. I went to West Marine and bought reinforced pvc tubing rated for hot or cold water.



I pulled the new tube through the position of the old one I was replacing.

I had to contrive the end fittings from hardware store parts. It was impossible between Home Depot, a plumbing supplier, and a high quality hardware store to find fittings that can be screwed on without removing a hose from a barb. The Quest tubes are conveninent this way. Perhaps Pex, though the Pex I sampled at Home Depot felt too stiff to make the various snaking turns.

Perhaps in the future if I have a similar project and less urgency I will get Quest again instead. The fittings are sold on Amazon. There are of course, people on the internet who say this is a bad idea.

Once the tube was in (with the water heater tank removed and looped closed) Voila! The pump stopped when I turned the faucet off.

I buttoned the floorboards back up, reinstalled the holding tank, and tomorrow, will reconnect a new hot water tank....

Good find and resolution. Now consider that the rest of the hoses are the same material and the same age.

Oh that is all glorious and useful and sends a sensation of success across all our furrowed brows.