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Friday, November 1, 2024

A better fresh water pump!

How to revive a failing water pump
(and make it better!)

This is a companion blog article to a YouTube video we did on the same topic.


Disclaimer: You must be electrically and mechanically competent to complete these repairs/upgrades.  If you are unsure of any step, stop and get professional assistance.  You can always reach out to me and I will try my best to help.


Our Vision 444 ES catamaran uses two freshwater pumps, one in each hull.  Each one is a 24V diaphragm pump made by Pentair.  Don't worry, the same steps apply to 12V pumps.

We have one in each hull, but we also have crossover valves, which when we open, allows one pump to pressurize the water on both sides.  We normally operate them this way so that we drain water from one tank, then we can switch which pump is powered up and pull from the other tank.

About a year after we launched, the port side pump started acting up.  It would sputter and get sporadic in running as it got close to the cut-off pressure.  It was very obviously sounding different and on it's way out.

I came up with a solution, applied it, and it has been successfully running for about 6 months now, so I wanted to share my solution!

The Problem

Too much is being asked of the little switch that sends current flowing through the pump motor. It's actually a high quality Omron switch, but DC motors suck a lot of current when first turning on, so the contacts in the switch end up arcing as the pump cycles on and off. That's okay, but it does degrade the life of the switch. The switch is rated for only so many electrical cycles (the number of mechanical cycles are rated too, but that takes a looooong time).  When the current is increased, the number of cycles the switch can sustain is reduced.

The Basic Solution

So, the switch fails, you repair it, right?  Yes and no. Okay, yes obviously, but the switch is not made to be or sold by Pentair as a replacement part. You have the replace the entire "Upper Assembly"(94-801-10, which sells for about $60, when the only problem is a $3.50 (or $17 for 4) switch!  

SHURflo AquaKing II - image copyright Pentair


Note, these steps and parts are for the Pentair SHURflo AquaKing II 24V, 5.0 GPM pump (4158-163-A75/E75).  These are likely the same exact steps for the 12V version of this pump and also others in the family that have a lower GPM rating.  Reach out if you are not sure!

Replacing Just The Switch

Parts

So, if you want to replace the switch by itself, you will need the following:

  • New Switch - Omron - V15-2C26-K (Check yours first)
  • Soldering Iron
  • Solder
  • Rosin soldering flux (highly recommended)
  • Screwdriver (Phillips)
  • Optional
    • You may need some crimp connecters to re-install the pump to your boat.
    • We try to keep a spare of just about everything.  Not a bad idea to have an upper housing spare on the boat anyways, and if this repair goes sideways, or you loose a part, you will still be able to repair the pump using that!

These are the three screws that hold on the switch housing

Steps

  1. Remove the pump from the boat
    1. Un-power the pump (switch, breaker or fuse, depending on your boat)
  2. Drain water/pressure from your freshwater system by opening a low water outlet (sink, shower, etc).  Leave this open while you work.
  3. Remove the water connection
  4. Remove the electrical connection (this may require cutting wires)
  5. Place the pump where you can work on it and don't mind some residual water draining.
  6. Remove the three Phillips screws that are holding on a small cover on the Upper Assembly.
    1. There are quite a few parts inside that will fall out. They are easy to re-install, just don't loose them!
    2. One screw is longer and goes through a longer section of the cover you are removing.
  7. Carefully work the switch out of the plastic housing.
  8. When out, work the rubber insulation boot about 6 inches down the insulated wire.
  9. Remove the slide-on connector from one of the switch contacts.
  10. Unsolder the wire from the remaining switch connector.
  11. While the wire is hot, re-solder this wire onto the equivalent contact on your replacement switch.
    1. Flux and a high wattage iron will help a lot. Be careful not to touch anything with the tip of the hot iron and have a safe place to reset it when not using it!
    2. Turn off your iron when done and place it somewhere safe to cool.
  12. Slide the other connecter onto the new switch.
  13. Slide the rubber boot down the wires and up against the switch.
  14. Slide the switch and rubber boot back into the housing.
    (There are rails and grooves that mate with one-another).
  15. Re-assemble the switch and cover to the pump upper housing.
    1. Make sure the beige rubber plug is fitted flush into the pump upper housing.
    2. Place the three screws through the switch housing.
      Make sure the long screw goes through the thickest portion of plastic.
    3. Place the small, round plastic plug (shaped like a top-hat) into the switch housing hole, on to the top of the adjusting set screw.  The skinner button portion of the plug should face out.
    4. Insert the pressure spring into the same housing hole.
    5. Place the gasket onto the screws, aligning the shape of the gasket to match.
    6. Place the black plastic lever into the intermediate plastic piece.
      It can only fit one way.  The bump on one end of the lever will align with the button on the switch.
    7. Carefully slide the intermediate piece and lever onto the screws of the switch housing and gently squeeze together. You would be able to manually activate the switch using the part of the lever that will mate with the beige rubber plug.
    8. Make sure that everything seems to fit together well.  
    9. Place this against the pump housing and carefully screw in all three screws, while holding the pieces tightly together (so nothing can more out of place).
    10. Snug the three screws with modest pressuse- they are just in plastic.
  16. Reinstall the pump into the boat, connecting the water connections, electrical connection and tightening the mounting screws.  
  17. Apply power to the pump.  It should start to operate, and since you have a tap open, you will be able to work the air out of the system.  Do not close the tap until you expel the air pocket that was introduced.
  18. When you close the tap, the pump should run for no more than 10-20 seconds, build pressure and turn off.  If it does not, open again and make sure there is no more air in the system.
  19. If it still does not turn off, you may need to adjust the pressure cut-off set screw with a 2mm allen wrench.
    If you need to loosen this screw by more than half a turn, something else is wrong, recheck everything and if no luck, reach out to me!
  20. Double check that your water connections are not leaking and that there are no leaks around the switch housing.  If there are, snug those three screws a little more.
  21. DONE!
Check out the YouTube video to see how bad our old switch looked internally!

The Advanced Solution

Why You Need It

The advanced solution is highly recommended if you are a live-aboard, or just want a more robust solution that will likely never require another switch replacement.

Unless you pump is lightly used, I would suggest starting by replacing the switch, as detailed above. 

The proper solution, is to allow that small micro-switch to operate within its designed parameters. In order to do that, we will have to insert another device which handles the high current, while the micro-switch simply tells this device when to turn on.

How To Accomplish This

Some of you are probably thinking relay! Yes, it is a relay, but a specialized type of relay.  Relays, at least electro-mechanical relays, ultimately have the same contact arrangement as the micro-switch, just larger and hopefully better able to handle the motor current.  It will take a lot longer, but they will succumb to the same contact erosion and eventual failure.

The solution I prefer is to use a Solid State Relay (SSR for short).  From the outside, these work just like the electro-mechanical versions, however internally, they are quite different.  The current switching is being done by a semiconductor called a MOSFET (Metal Oxide Semiconductor, Field Effect Transistor).  Apply a small charge to the "gate" of the MOSFET and the PN junction will then "open" and allow electrons to flow.  This is really the basis of how every semiconductor works.

E-T-A Solid State Relay - image copyright E-T-A

At any rate, when the electrons are allowed to flow, they are not having to jump across any tiny air-gap, so there is no arc, therefore there is no erosion taking place and the MOSFET will survive indefinitely, as long as the maximum amount of current does not exceed it's rating (which has to do with channel width in the silicon).

TLDR - A properly sized SSR can be switched by an incredible small current from the micro-switch and allow the large motor current to flow without sustaining damage!

Adding in an SSR

Parts

In order to perform this upgrade, you will need the following:
  • SSR - This will vary based on the voltage and fuse fating (as shown on motor) of the pump you have.
  • Wire cutters
  • Wire stripper
  • Wire connector crimper
  • Female, 0.187" crimp quick-connect insulated connectors for small tabs on SSR.
  • Female, 0.25" crimp quick-connect insulated connectors for large tabs on SSR.
  • 6" Length of marine wire, Red, 12 or 14 gauge (to match the red wire gauge on your pump)
  • 6" Length of marine wire, Black, 18 - 22 gauge (carries almost no current)
  • Soldering Iron
  • Solder
  • Soldering flux
  • Two 1" long pieces of heat-shrink tubing, large enough to slide over two pieces of pump motor wires laid on top of each other.
  • Lighter or heat gun to shrink heat-shrink tubing.
  • 6-8" piece of electrical tape
  • Optional
    I'm a big fan on using these same Quick Connectors when you re-install the pump into your boat.  It is so much easier to take the pump out to replace any items, and if you use Quick Connect connectors, this becomes so much easier.

Diagrams

Okay, a couple pictures, will hopefully make this make better sense.

First, this is how the pump normally works in your system:

Standard Water Pump Configuration
Standard Water Pump Configuration

Preparing Water Pump for SSR

SSR Water Pump Configuration

The quick description of the process is that we cut the wire coming from the switch to the motor and insert the SSR so that high current flows from the boat, through the switch portion of the SSR and into the motor.  The control side of the SSR is powered by the signal coming from the small switch inside the pump housing and we also provide a return path for that switch current back to the boat negative.

Steps

  1. Remove the pump from wherever is is mounted, following steps 1 through 5, above.
  2. Cut the red wire that goes from the switch to the pump motor, about in the middle.
    1. Strip about 3/16"-1/4" of insulation from the end and crimp a 0.187" tab, female quick- connect connector to the wire coming from the switch.
    2. Strip about 3/16"-1/4" of insulation from the end and crimp a 0.25" tab, female, quick- connect connector to the wire going to the motor
  3. Create a gap in the insulation on the main red and black wires that used to be connected to your boat, as follows: *See below for a tip on how to do this
    1. Red wire that is going to the switch, place the gap at about the same length from the switch as where the other red wire was cut.
    2. Black wire that is going to the motor, place the gap so that it will be close to the opening in the red wire however the pump was mounted and wire strung in your boat.
  4. Take the 6" length of red wire, strip one end about 1/2" and wrap around the exposed conductor in the gap of the red wire.  It should make at least one full revolution.
    1. Solder this connection, making sure the added wire cannot "spin" around the original wire when complete.
    2. Slide heat shrink over this connection and carefully apply heat to shrink onto wire.
  5. Take the 6" length of black wire, strip on end about 1/2" and wrap around the exposed conductor in the gap of the black wire.  It should make at least one full revolution.
    1. Solder this connection, making sure the added wire cannot "spin" around the original wire when complete.
    2. Slide heat shrink over this connection and carefully apply heat to shrink onto wire.
  6. Cut the 6" wires shorter, if desired.  This will allow the SSR to be connected in, without excess wire length.
    1. Strip about 3/16"-1/4" of insulation from the end of the red wire and crimp a 0.25" tab -female quick-connect connector to this wire.
    2. Strip about 3/16"-1/4" of insulation from the end of the black wire and crimp a 0.187" tab female quick-connect connector to this wire. 
  7. Attach the four wires as follows:
    1. Small (0.187") connector on the red wire to pin 1.
    2. Small (0.187") connector on added black wire to pin 2.
    3. Larger (0.25") connector on added red wire to pin 3.
    4. Larger (0.25") connector on red wire going to motor to pin 5.
  8. Wrap a few loops of electrical tape around the bottom of the relay and the connectors to secure and insulate everything.
  9. Optional: As mentioned above, I'm a big fan of adding these same style connectors to the wiring connection between the boat and the pump.  If you want to do that:
    1. Strip the end of the red and black wires on the pump and the boat by 3/16" - 1/4".
    2. Crimp FEMALE quick-connect connectors to the red and black BOAT wires.
    3. Crimp MALE quick-connect connector to the red and black PUMP wires.
  10. Re-install the pump into the boat, following steps 16 to 20 above.
  11. Once you are happy with everything, consider using a nylon tie to secure the relay and wires into a nice tidy bundle adjacent to the motor of the pump.

Pin Assignment for SSR

Pin assignment from E-T-A Datasheet - copyright E-T-A

That's a Wrap!

Whether you use your boat on the weekend or live-aboard full-time, you want to be on your boat enjoying yourself, not doing unexpected work.

To me this is a perfect example of investing a little time and expense on your terms so that your enjoyment is ruined (usually at the worst possible time - I think that should be called Neptune's Law) 

I hope you enjoy this tutorial and it all made sense and was easy to follow. If not, please take a moment to let me know via comment so I can fix it.

Also, please leave a comment if you put this into place and tell me how things went!



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Location: Mt Hartman Bay, Grenada
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