Water System Problems

[wrwakefield]

Supplemental info to above post: I just found an overview spec sheet for the Marco water pumps being discussed.

FYI, Bill

[Benz]

"Normal flying...." I though economy WAS normal flying. We must be from different worlds.

[Dockhead]

Originally Posted by sailorboy1

. . . I of course will now never have a problem because I have a spare on the boat that has not been out of the box.

It's amazing how that works.

I have two Whale Gulper gray water pumps on board which are original to the boat, so more than 20 years old. I've replaced a few diaphragms in one of them (before figuring out that chlorine kills them), but otherwise flawless over all those years. The only possible explanation is the fact that I have a complete new spare in a box on board.

[Dockhead]

Originally Posted by Benz

"Normal flying...." I though economy WAS normal flying. We must be from different worlds.

Not when it's a 13 hour flight!!

[Dockhead]

Originally Posted by HopCar

The two most common problems I’ve seen on water system pumps are bad switches and bad valves. Pick a good pump and buy two of them. Buy a spare switch and valve set. Install the new pump in a way that makes it easy to exchange. When the pump dies, just swap it for the new one and repair the first one when you have time.

That's of course a classic approach and undoubtedly good advice.


I'm attracted to the external switches, however, because they have vastly larger contacts. They are not expensive, and much easier to swap out than pulling the whole pump.


And in general -- why should this be so much trouble? I did decades of sailing on two different boats and never had the slightest problem with the pressure water systems. Then a few years ago it started and hasn't let up since. Bah!

[Dockhead]

Originally Posted by rslifkin

Most pumps have crappy pressure switches that don't hold up and either fail to power the pump or they start sticking on. Either use an external one, or add a relay so the internal switch only has to carry the relay coil current and not the full load of the pump motor. That generally makes them much more reliable, as the tiny contacts are no longer subject to the same abuse.

I hadn't thought of a relay. That's a great idea.

[Dockhead]

Originally Posted by wrwakefield

Supplemental info to above post: I just found an overview spec sheet for the Marco water pumps being discussed.

FYI, Bill

The Marco pumps are sold by my usual online chandler, SVB24 in Germany.

These look very well made, and I get the advantage of variable speed.

No expansion tank is needed, so installation is super simple.

They are pretty expensive -- 15l/h model costs about €300. So two of them would be €600.

Could I bet on the small pressure switch holding up long term? Unlike the case with a normal pump, I won't be able to use an external switch with this one, if the switch fails. FWIW, the Marco pump has a pressure switch which looks very different from the tiny microswitch deal in conventional pumps.

Or do I go with the external pressure switch, somewhat more complicated plumbing, but then easily use any of my existing pumps.

Hmm.

[rslifkin]

The only thing that has kept me away from the Marco pumps in the past is that they're fairly low pressure. To make up for a fairly restrictive set of filters, I run my system at the pump / pressure tank in the 40 - 60 psi range (pump cut in/out pressures). Most of the Marco pumps don't even reach 40 psi, let alone higher.

[Dockhead]

Originally Posted by rslifkin

The only thing that has kept me away from the Marco pumps in the past is that they're fairly low pressure. To make up for a fairly restrictive set of filters, I run my system at the pump / pressure tank in the 40 - 60 psi range (pump cut in/out pressures). Most of the Marco pumps don't even reach 40 psi, let alone higher.

Yeah, 2.5 bar. Do you think that would significantly reduce flow rate? I don't have filters in my system.

[rslifkin]

With no filters in the system I doubt you'd have trouble getting enough flow at the lower pressure. Worst case you might need to switch to higher flow aerators in the faucets.

In my case, with 2 gpm of actual flow through the system, I've got about a 10 psi drop across the filters (and that's based on the specs for clean filters, so it may be a little worse once they've been in use for a while). Higher flow rates (which is rare for us) would show even more pressure drop. I'm running the water through a 1 micron sediment filter, a granular carbon and KDF55 cartridge and then a 0.5 micron carbon block (all in 4.5x10 housings).

[Dockhead]

Originally Posted by rslifkin

With no filters in the system I doubt you'd have trouble getting enough flow at the lower pressure. Worst case you might need to switch to higher flow aerators in the faucets.

In my case, with 2 gpm of actual flow through the system, I've got about a 10 psi drop across the filters (and that's based on the specs for clean filters, so it may be a little worse once they've been in use for a while). Higher flow rates (which is rare for us) would show even more pressure drop. I'm running the water through a 1 micron sediment filter, a granular carbon and KDF55 cartridge and then a 0.5 micron carbon block (all in 4.5x10 housings).

OK, thanks. It could be worth a try.

We have two showers, three sinks, one fresh water toilet, and a washing machine. The last pump was a Johnson 3.5 WPS, with a flow rate of about 12l/m, a size smaller than the original, and while the pressure and flow was less, it was enough.

Alternatively, install an industrial-quality pressure switch, which cost about €150, with MTBF of millions of cycles, and call it done. Use any pump.

It irritates me that the pumps made for this use don't have switches designed for the duty. We shouldn't have to resort to using industrial quality kit. All of these systems -- using standard yachting parts -- should be extremely reliable over a reasonable useful life, not like this.

[rslifkin]

Originally Posted by Dockhead

It irritates me that the pumps made for this use don't have switches designed for the duty. We shouldn't have to resort to using industrial quality kit. All of these systems -- using standard yachting parts -- should be extremely reliable over a reasonable useful life, not like this.

Agreed. The Jabsco washdown pump (hotshot HD4) I'm using as a water pump is great as a pump, but the pressure switch is crap. The first one started sticking within a few months. I added a relay when I replaced it which resolved the reliability issue. But as it reaches shutoff pressure it has an annoying chatter. That can't be good for the pump, and it's definitely a factor in the original switch failing (that one did it too). With the big pressure tank in my system I think the pressure just doesn't rise sharply enough to definitively trip the pressure switch off, so it chatters on and off a couple times before it really decides.

I might go to an external pressure switch to fix it, but I've got the challenge of figuring out where to plumb it into the system unless I can find a sealed / ignition protected switch to use (gas boat, water pump and such is in the engine room).

The old 1980s Shurflo I had before I rebuilt some of the water system was only the second one in the boat's life. Each lasted 15+ years. Oddly, the tiny pressure switch in those pumps was dead on reliable.

[Dockhead]

Originally Posted by rslifkin

Agreed. The Jabsco washdown pump (hotshot HD4) I'm using as a water pump is great as a pump, but the pressure switch is crap. The first one started sticking within a few months. I added a relay when I replaced it which resolved the reliability issue. But as it reaches shutoff pressure it has an annoying chatter. That can't be good for the pump, and it's definitely a factor in the original switch failing (that one did it too). With the big pressure tank in my system I think the pressure just doesn't rise sharply enough to definitively trip the pressure switch off, so it chatters on and off a couple times before it really decides.

I might go to an external pressure switch to fix it, but I've got the challenge of figuring out where to plumb it into the system unless I can find a sealed / ignition protected switch to use (gas boat, water pump and such is in the engine room).

The old 1980s Shurflo I had before I rebuilt some of the water system was only the second one in the boat's life. Each lasted 15+ years. Oddly, the tiny pressure switch in those pumps was dead on reliable.

The original Shurflo pump in my boat lasted from 2001 until 2017 and died due to a rusted bearing. The pressure switch, like the pump, lasted 16 years and never missed a beat. I've had THREE different pumps in the boat since 2017 and all three are dead, all of them because of pressure switches. This is completely ridiculous, and I really resent all the time I've spent futzing with pumps these last years. Not so much the money I spent on them as all the cruising time lost, with my head in the bilges in some beautiful place in the brief, precious Nordic summer days, while my crew was out enjoying themselves. Bah.



In that context, €150 for an industrial-quality external switch with a million+ cycles MTBF seems like a bargain. The replumbing required is not that big a deal. And as to the time spent working on it -- 10 hours of work in the off season is worth one hour during a cruise, in my book.


As to your application -- I am more than certain that these exist in ignition-protected versions. They are used in plants handling gas, for example. This one looks pretty good: https://www.fisheriessupply.com/groc...ressure-switch

[Dockhead]

It strikes me that one of the inherent challenges in these designs is the high amperage inductive load being switched. I've looked through quite a lot of spec sheets of industrial pressure switches, and they are rarely rated for more than a couple of amps. So it looks to me that a correct installation would need a solid-state relay and flyback diode. I installed a solid-state relay and flyback diode in my autopilot setup many years ago, to protect the relays in the autopilot computer box.


The Marco pumps are electronically controlled, so the pressure switch will not be switching the whole motor current. This is inherently better I think, albeit more complex.

[rslifkin]

It doesn't necessarily need a solid state relay, just a relay with sufficiently beefy contacts. Generally if you use a relay rated for significantly more than the power draw of the pump you'll be fine. My washdown pump has a 30A fuse and uses a 70A relay (the ones with larger connector pins than the common 1/4" stuff). Water pump is on a 15A breaker and has a 50A relay.

The relay on my fresh water pump is this Fastronix kit: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1