Water pump keeps running on Mainship 390 for no reason

My water pump keeps kicking on every 20 minutes or so for about 3 seconds.
The manual states this indicates a leak. There's not much to check. The forward and aft shower's. The bathroom sink and shower. The water heater. I don't see anything. I live in the Fort Lauderdale area and have been very disappointed whenever I have needed work done (Besides Wards Electric). Does anybody know somebody good in the area?

If no leaks...and they can literally be a few drops...

Then many times it is internal bypass within the pump. If that, you can rebuild or replace the pump end or the whole pump.

Every 20 minutes isn't bad unless it wakes you up. It might stay like that for many months if you can stand it.

Shut it off until you need it?

If you have a pressure tank, check the bladder air pressure. Loss of air in the bladder may be making the pump short cycle. You still have a leak to find, but most pumps with pressure tanks run for more than 3 seconds.

Ted

What make/model pump is it? Most will have a pressure switch of sorts that detects when pressure drops and will run the pump accordingly. If that switch is broken it'll cause the pump to run. But there's a ton of places where something can leak.

What kind of piping is in the boat? The push-fit Whale style? Might be an easy way to check the pump by stubbing off the out side with a valve. That'd narrow it down, right quick.

I bet it's the jabsco pump. They tend to leak internally. I've had several and tried replacing the pressure switch with no avail. The final solution was to avoid jabsco products

That run time indicates a steady dripping leak externally.
Check the water heater relief valve and all around the base of the water heater for dampness.
Is there any trail of water leaking into the bilge? Get a bright light and check everywhere there is plumbing, not just at the end equipment.
Also could be an internal pump check valve leak as mentioned above.
Do you not have a galley sink? Ice maker? Shower on the transom?

Its not just Jabsco, I have had at least 4 different manufactures including Shuflo, Seaflo, Five Oceans...... forgot the other (s).....

Now whether they are all clones under different names....or have the same parts in the pump sections I cant say....

But the one or two second burps are often the inyernal bypass after completely sure you dont have a leak....including electric toilets, etc....

Next O' nite or when you leave the boat, turn off the pump.

On return ,switch pump on and monitor, if its a system leak the pump will run for a while, if it an internal leak the run time will be short .

Hunt down the accumulator, try bleeding from the tire valve stem. If you immediately get water and no air, the accumulator has failed. Replace the accumulator If you get air, a few strokes with a hand pump to replace the pressure you bled off. Onward in your trouble shooting.

Good advice FF.

Is there even an accumultor in the system?

The most common cause of this is the internal check valve on the inlet side of the pump. Water leaks back into the tank past the check valve and the pump comes back on to build pressure. It can rive you crazy as it is a leak with no visible water loss at all.

Greetings,
Mr. PB. Can't add anything to the good suggestions already posted BUT I am also looking for competent trades people in FLL. Many, many good businesses there with helpful and very competent counter staff BUT no field workers that are worth the extortion of $100+/hr rates charged. I don't mind high fees but please send someone, ANYONE who knows which end of a screwdriver to use...

RT Firefly said:

Greetings,
Mr. PB. Can't add anything to the good suggestions already posted BUT I am also looking for competent trades people in FLL. Many, many good businesses there with helpful and very competent counter staff BUT no field workers that are worth the extortion of $100+/hr rates charged. I don't mind high fees but please send someone, ANYONE who knows which end of a screwdriver to use...

Click to expand...

Where abouts in FL and what do you need done? I maybe able to recommend a few folks.

RT, you meant to say, "$100 PLUS"
I learned my lesson when it comes to 'shade-tree' mechanics and one boatyard.

You can prove the check valve condition by immediately after it pumps up, close the tank outlet and remove the pump inlet hose. The water should drain out of the pump and stop. If it keeps draining then the check valve(s) are leaking.

If no sink/shower leaks, it's the pump valves leaking. Water leaving the pump goes thru a check valve. The valve holds pressure for the whole system after the pump shuts off.
If the valve seal is bad, and it could be as simple as a piece of debris embedded in the seal, water will slowly leak back to the pump water source.

I had the same problem a few years back and found that all that was needed to stop the intermittent running was to snug-up all the hose clamps on the water lines from the pump downstream. Not sure which one was the culprit, but some did tighten significantly during the procedure.

OldDan1943 said:

Where abouts in FL and what do you need done? I maybe able to recommend a few folks.

RT, you meant to say, "$100 PLUS"
I learned my lesson when it comes to 'shade-tree' mechanics and one boatyard.

Click to expand...

My boat is docked behind a private residence in Lauderdale Isles. I have a bilge pump that doesn't get all the water out. We plan on going to the Bahamas in January for 6 months or so, so I'm looking for someone to show me how to change impellers, do oil changes and change filters. Only had the boat since July. Whenever i have had someone to "fix" something they spend hours without rectifying the issue.

Greetings,
Mr. PB. Do you have engine and/or equipment manuals? IF you can find a comfortable place to sit beside the engine or in the engine space, have the engine manual at hand as well as an inspection mirror and a GOOD source of light and imagine going through the steps to perform various service tasks.



If changing impellers, for example, what tools will you need? Is there anything in the way that has to be removed before you can change an impeller? Can you actually see and reach everything you have to? When you drop your wrench or a screw/nut/bolt, where will it end up? That sort of stuff.

Paul Baker said:

My boat is docked behind a private residence in Lauderdale Isles. I have a bilge pump that doesn't get all the water out. We plan on going to the Bahamas in January for 6 months or so, so I'm looking for someone to show me how to change impellers, do oil changes and change filters. Only had the boat since July. Whenever i have had someone to "fix" something they spend hours without rectifying the issue.

Click to expand...

Sounds like a shout out for help from a local TFer. Anyone in the neighborhood?

Had a similar problem caused by a faulty fresh-water valve for the toilet. Fortunately, it eventually corrected itself.

Greetings,
Mr. HW. Not until the fall (Oct./Nov) although I don't think I'd be much help other than moral support...

Folks, seldom do I write this much about so little. If you will indulge me this ONE time event. Get a cup of coffee and get comfortable.
I consider the FW water pumps, accumulator and compartment fans as expendable items.
If you determine the the pump on the fresh water pump is bad due to an internal leakage or a pressure switch, replace the whole thing. First you have to trouble shoot the system to determine what part of the FW system is bad. Ya'll are nit picking over basically 'nothing'. Now, if you/we are discussing this as an "exercise", discuss away. In this case we have the luxury to discuss the possibilities. If you are on cruise and have this problem, you can live with it, fine. You can say, "I will have the pump parts to repair the pump." Do you have a spare motor too? I expect you to reach into your parts locker, find the brand new FW pump and motor, spend an hour replacing the entire unit. Historically, some folks install a second installed pump. They change the valve line up, flip a switch and presto, they are on a new pump in a matter of minutes. There was one guy, in another thread, who admitted, he had a FW water pump failure and no spare. He could not, according to him, get the FW out of the tank. I can only guess he didn't have a fresh water tank drain or didn't know he had a drain. I have a drain with a valve. Think how your guests, wife or 'special someone' would react to a FW pump failure. He could not get the FW to flush the crapper. Get a second FW pump. Change it over and be done with it. Save the other pump if you wish, maybe even disassemble it. You get back to port, call the company, order all the internal pump parts if that makes you happy. Spend all the time in the world rebuilding the dead pump and pressure switch if that fulfills your dreams. Me? That is not one of my dreams. Redundancy for pumps and compartment fans and a bunch of other things makes for a happy cruise. I brought my Nordhavn down from Long Island to Miami with 2 adjustable wrenches, 4 screw driver, channel locks plus one or two other tools, never using any of them. All of us want each and every cruise to be comfortable. We do not want to spend our time in the holy-place during the cruise except to check the oil level and coolant level. We cannot plan for every possible failure but we can plan for the common failures. We all carry impellers and ideally some spare belts for the generator and main engine. If you dont have belts and impellers buy them and at least plan on how to replace them. Toss in spare radiator caps, spare alternators too. You carry spare oil I hope. Maybe not enough for an oil change but maybe a couple of quart cans or a gallon so you can add to the oil, if necessary. So the same with the anti-freeze. We all carry multiple fuel filters and filters for the water-maker. For those of us with one engine, we carry a couple of towing service insurance companies.
Now, I shall shut up and watch how the nit-picking, trouble shooting progresses.
Let us not worry about the small chit. Keep the 'down-time' down and enjoy the cruise.
One other thing, carry some extra common sense in the spare parts locker too.
We worry about each other and will even share our spare parts if we are cruising together.

Paul Baker said:

My water pump keeps kicking on every 20 minutes or so for about 3 seconds.

The manual states this indicates a leak. There's not much to check. The forward and aft shower's. The bathroom sink and shower. The water heater. I don't see anything. I live in the Fort Lauderdale area and have been very disappointed whenever I have needed work done (Besides Wards Electric). Does anybody know somebody good in the area?

Click to expand...

Mine did that also and finally determined it was not a leak, it was the ice maker cycling and filling up. Once the ice bin was full, it stopped. Probably unique to me but worth checking if you have an ice maker.

I had the same thing happen to me about 6 months ago. It turned out it was a leaking hose where the clamp was....very very small lead...only a few drops or so at a time. I would go around and check all of your clamps and change any that need changing...good luck

Do you have an ice maker? If so, try turning it off. If your pump stops cycling, then you know...

Mine cycles on a similar cycle until it's full of ice.

OldDan1943 said:

Hunt down the accumulator, try bleeding from the tire valve stem. If you immediately get water and no air, the accumulator has failed. Replace the accumulator If you get air, a few strokes with a hand pump to replace the pressure you bled off. Onward in your trouble shooting.

Click to expand...

You can also put your hand on the side and feel the temp change. The water will be cooler than ambient usually. If you feel the same all the way up, chances are good you'll get water out of the valve stem since the bladder is flat.

I had the same problem when I got my MS 400. As per a previous post, I checked the tire pressure valve and got water out: bladder was shot. Changed it out and the problem was fixed.
If that isn't the problem, I think like the 400, the 390 has a water manifold. Try turning off all the lines at the manifold to see if the problem stops. If it does, you have a small leak somewhere down line. If it doesn't it is between the tank and the manifold, most likely the pump. Also, make sure it isn't the outside "RV" water connection.

Check all of your internal plumbing for slow leaks, particularly where there may be joints between sections or on the back side of faucets. You can probably spot any "wet spots" in the bilge if you don't normally expect water to be there.

I had cycling water pump caused by a slow leak that I chased for three months before I found it. One of the previous owners had installed a small "repair" section of potable water-grade tubing inline with the factory PVC piping. The section was under my removable bilge cover sections and practically right on top of the main bilge pump. I realized that it must be a leak when I would periodically hear the bilge pump cycling at the dock (I use the boat as my city "boatpartment" three nights/week). I finally found the drip, tightened the loose clamp which had caused the problem in the first place, and problem solved. I'm gradually replacing all clamps on the fourty-two year-old Grand Banks 42 which are intended to keep water out or keep water in, and double clamping nearly everything with solid-band SS clamps.

Water Pump Issue

I had the exact same issue. It was a Jabsco variable speed pump that was the issue. I replaced it with another pump and have no issues.