Mach5 pump

[x2y3z4]

A few nights ago, the pressure water hose on our Headhunter Mach 5 freshwater pump had come loose.
After about 10-15min I had turned it off and fixed the misery.
After I reattached the hose, now with two new hose clamps, the pump no longer stops. It builds up a pressure of about 60PSI, but not that much to shut off (66).
I have searched the entire boat and found no leak in the fresh water system. The Mach5 is not leaking either.


Our 24V pump is operating normally. However, this is building less pressure to shut off.
I have checked to see if there is air trapped or other air leaks - to no avail.

What could be the cause?

 

[STB]

I suspect that there is a leak that you have yet to find, because that is almost always what I find.

The easiest ones to miss are often those that leak into their own sump, such as a shower or bathtub faucet, or a dishwasher or clothes washer slightly dribbling inside when a valve doesn't fully shut; those faucets or spigots that are outside such as a deck shower, anchor washdown, deck washdown, etc; those leak from a hidden place into a hard to access place, such as washdowns that leak from within a gunwale or a hard to spot corner of the laz, or the front of the anchor locker obscured by a pie of chain, rope, and machinery; or appliances that drain overboard, such as watermakers. I'm betting on something like this.


But, it could also be a bad pressure switch within the pump (unless you've measured); a weak pump; a failed expansion tank very slowly losing its air; a leak from the hot water heater into the engine's coolant loop, if connected (and you'd be "making" coolant, possibly in an overflow or dripping from cap or overflow to bilge); a misbehaving watermaker leaking water overboard, or a bad backflow valve within the pump allowing the pressure to vent toward the tanks when the pump goes off (except that you report that it never goes off, but is never really never, or just briefly?)

Note that "bad" pressure relief valves, "bad" backflow preventers, etc, may be scaled or obstructed by debris in potentially reversible ways vs otherwise broken.

Happy hunting!

 

[tiltrider1]

Clamp the hose close to the pump.
Does it turn off now. If yes you have a leak. If no you have a pressure sensor failure.

 

[cafesport]

You need to bleed the air out when restarting a Mach 5 after such a repair. Shut the pump off and completely depressurize the fw system. Leave the highest elevation outlet wide open. Turn on the pump and once the pressure rises to 60 or so you should be able to close the valve. The pump should make a pretty horrible sound on start up for about 5 seconds before it starts flowing at max flow. One other thought running for 15 mins at 10 gpm could have emptied your water tank mimicking a suction leak.

 

[STB]

Clamp the hose close to the pump.
Does it turn off now. If yes you have a leak. If no you have a pressure sensor failure.

My only concern with this method is that you've got to /really/ clamp the hose well and that is easy to get not quite right and I always feel badly about doing it to a perfectly good hose.

I'd recommend making a stub with a plug.

Having said that, I've never made a stub with a plug. I have done /almost/ as tiltrider1 suggests. Ive disconnected the hose at the next connection and folded it over near the pump and clamped it at the fold. Poor hose. I've always replaced them shortly thereafter out of guilt.

 

[RickyD]

A few nights ago, the pressure water hose on our Headhunter Mach 5 freshwater pump had come loose.
After about 10-15min I had turned it off and fixed the misery.
After I reattached the hose, now with two new hose clamps, the pump no longer stops. It builds up a pressure of about 60PSI, but not that much to shut off (66).
I have searched the entire boat and found no leak in the fresh water system. The Mach5 is not leaking either.


Our 24V pump is operating normally. However, this is building less pressure to shut off.
I have checked to see if there is air trapped or other air leaks - to no avail.

What could be the cause?

I also have a headhunter. Getting all air out of the system as described above is important. I open all of the faucets to do this. Probably over kill but it works. Also, I had a leak that was almost impossible to find. I looked every where. Finally I pulled out the floor boards under the galley sink and there was a mist. The tiniest pin hole in a water line just created a fog. That solved it until I redid all of the hot water pipes. Leaks like this come generally from old pipes and hot water pipes die fastest. I love my Headhunter. Weird name, works great. i know, head like toilet.

 

[twistedtree]

I agree with others about trapped air being a likely cause, especially into any hot water tank/heater.

To test for leaks, let the pump run to some reasonable pressure, then turn it off. Pressure should hold indefinitely. If it’s drifting down then you have a leak of some sort.

 

[x2y3z4]

One other thought running for 15 mins at 10 gpm could have emptied your water tank mimicking a suction leak.

...exactly, because it was at the same time a good test for our bilge pumps and our IoT alarm system (to which I added another alarm siren the following day)

 

[twistedtree]

...exactly, because it was at the same time a good test for our bilge pumps and our IoT alarm system (to which I added another alarm siren the following day)

So was this the problem?

 

[x2y3z4]

I followed all the advice, thank you very much!

First step: we have finished the global hunt. No leak, at least none found.

Second step as recommended: I let the pressure out of the system one more time and disassembled the hose. Then built up pressure. Then released the pressure again this time at the highest tapping point. Then let the air escape from this tapping point.

Third step: While the pump is running, I have opened all, really all water tapping points one after the other and let them run longer for a while.

The result is that the pump no longer runs permanently. That is at least a partial success. But it still turns on every 5 minutes without any tap having been opened.

 

[Delfin]

I followed all the advice, thank you very much!

First step: we have finished the global hunt. No leak, at least none found.

Second step as recommended: I let the pressure out of the system one more time and disassembled the hose. Then built up pressure. Then released the pressure again this time at the highest tapping point. Then let the air escape from this tapping point.

Third step: While the pump is running, I have opened all, really all water tapping points one after the other and let them run longer for a while.

The result is that the pump no longer runs permanently. That is at least a partial success. But it still turns on every 5 minutes without any tap having been opened.

I've had to run a lot of water through mine to get air out. So I'd suggest repeating the 'let 'er run' routine.

 

[twistedtree]

I've had to run a lot of water through mine to get air out. So I'd suggest repeating the 'let 'er run' routine.

I tend to agree. Even if you just use the water normally for a while, it should bleed air out over time.

It might also be worth a call to headhunter. Their tech support is pretty good, and they might have some ideas.

Also, if you plumbing allows, you could valve off parts of the system to see if there is some part that makes the cycling come and go. That might help narrow down what’s going on.

 

[Delfin]

You don't need it with a Headhunter, but I installed a small expansion tank. I think it helps performance as it keeps the pressure high enough to reduce cycling, including cycling caused by a bit of air in the system.

 

[Blewbird]

Dual Mach 5 pumps.

Had two of these plumbed in parallel with isolation valves and an overboard dump plumbed in for purging the pumps, then two large charcoal filters also plumbed in parallel with isolation valves, next in line were two large expansion tanks and finally a large ultra violet fixture. All on a large private yacht I worked before I retired. The dump valve made it a cinch to purge the pumps and with redundant pumps and filters it was easy to perform maintenance or trouble shoot. The large expansion tanks prevent short cycling of the pumps because the system was plumbed with PEX Pro which is rigid enough that no pressure is stored in the plumbing. No decision about cost or complexity when you are being paid to make an essential system work 100% of the time.

 

[HopCar]

One thing that causes a pump to turn on periodically is a slow leak back through the pump. If the problem continues, check the pump valves.

 

[x2y3z4]

I finally contacted Headhunter and their support answered in time (thumbs up), so far so good.
Their suggestions are like those I got from this forum.
And no changes at all: No leaks and no air. The pump won't stop, may stop for a short period like mentioned.
Because the 24V pump doesn't start during the night, I don't believe in leaks anymore.


We already had minor but nerv wrecking problems in the past when we ran our tanks empty, we now decided to give the Headhunter installation the final bullet.

And yes, we have a nice installation as well like "Bluebird" described: huge expension tank, plus pump paralleling with a 24V pump, plus UV cleaning etc.

The 24V pump never produced any headache, so the winter project will be to change over from Mach5 to a 24V-stacked/double-pump installation. We will parallel this to the existing 24V pump, put a relais in between and hope for install & forget.

Thanks for supporting!

 

[ronobrien]

Is it possible to pinch the outlet hose to see if that satisfies the pressure switch?