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Old 27-05-2019, 15:27   #1
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Water Pump Pressure Switch

So Iíve owned my boat for three years and Iím on my third freshwater pump. Iím annoyed and tired of spending money on expensive shoddily built pumps. The latest pump failure is a new jabsco variable speed pump. Itís having issues after a whole 2 months. The thing will prime the system after running an outlet and then just run continually at low speed. Anyway for $300ish Iím returning it.

So what my plan is, is to buy a belt driven jabsco diaphragm bilge pump (have one as actual bilge already and works great so far) and install that with a well pump pressure switch and accumulator tank.

The question is will a regular old Square D pressure switch work with 12v? I think it should because it looks like itís just a simple relay, and doesnít really care how many volts are being used. Am I correct in my thinking? Has anybody else gone this route before?
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Old 27-05-2019, 19:17   #2
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Re: Water Pump Pressure Switch

Do you have an accumulator tank now? I believe the shouldnít be used with variable speed pumps.
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Old 27-05-2019, 19:31   #3
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Re: Water Pump Pressure Switch

You will need to see if the specific Square D part is rated, or possibly de-rated, for 12VDC.


I have an old RV without a water pressure accumulator and it will cycle quite often. Previous owner put a switch in plain sight to turn if off when not in use.
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Old 28-05-2019, 04:43   #4
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Re: Water Pump Pressure Switch

Quote:
Originally Posted by meridian28 View Post
Do you have an accumulator tank now? I believe the shouldnít be used with variable speed pumps.
No I do not currently have an accumulator.

Quote:
Originally Posted by Spot View Post
You will need to see if the specific Square D part is rated, or possibly de-rated, for 12VDC.


I have an old RV without a water pressure accumulator and it will cycle quite often. Previous owner put a switch in plain sight to turn if off when not in use.
I thought about putting a switch near the galley sink, which is where the most on/off cycles of outlets occur. Then I thought that is sort of a bandaid and not actually fixing the root of the problem. I just want to build a system that works the way it should. Also this system will be easily serviceable as the pump can be rebuilt, and the pressure switch will be easily replaceable. Just have to find the correct pressure switch.
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Old 28-05-2019, 05:45   #5
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Re: Water Pump Pressure Switch

Quote:
Originally Posted by Kalimniosjohn View Post
So I’ve owned my boat for three years and I’m on my third freshwater pump. I’m annoyed and tired of spending money on expensive shoddily built pumps. The latest pump failure is a new jabsco variable speed pump. It’s having issues after a whole 2 months. The thing will prime the system after running an outlet and then just run continually at low speed. Anyway for $300ish I’m returning it.

So what my plan is, is to buy a belt driven jabsco diaphragm bilge pump (have one as actual bilge already and works great so far) and install that with a well pump pressure switch and accumulator tank.

The question is will a regular old Square D pressure switch work with 12v? I think it should because it looks like it’s just a simple relay, and doesn’t really care how many volts are being used. Am I correct in my thinking? Has anybody else gone this route before?

Most of the diaphragm pumps to be used for fresh water systems should already have a pressure switch built into the pump, so you should not need a separate pressure. Yes, you will need an accumulator tank. Depending on how well you want to dampen the pump pulses, look for one with a rubber diaphragm in it w/a Schrader valve to add air pressure behind it.

We used diaphragm pumps a long time ago, while very dependable tended to be much louder, pulsed more (even w/an accumulator) than the Flojet type pumps we currently use. Our pump has been in the system for years and been very dependable. Some of the symptoms of the continuous run sounds like a leak or air in the system, not allowing it do come to full pressure. Other causes could be debris getting past the filter (I assume you have a filter) getting into the pump head diaphragm or a clogged filter decreasing flow to the pump. We use a very large filter (similar to RO pre-filters) which have a very large capacity. A long shot could be your tank pick ups are clogged and starving the pump for water. If you have aluminum tanks and any chlorinated water been put in them, they could have a large amount of aluminum oxide chunks blocking the pick up.


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Old 28-05-2019, 08:58   #6
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Re: Water Pump Pressure Switch

Those pressure switches fail because of arcing. The starting loads of pump motors are much higher than running loads. Those switched are under engineered for the load. My solution has been to use a 40 amp automotive relay to handle the motor loads and control the relay with the pressure switch.

Headlight relays are rated for 40 amps and are cheap compared to a pump pressure switch. I carry a few spares. I use them on bilge pumps also. Since going this route I have not had a pressure switch failure. Sockets are also available making changing the relay a one minute job. The relays last for years. They are much more suited for the current demands than the switches that come with the pumps.
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Old 28-05-2019, 10:00   #7
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Re: Water Pump Pressure Switch

I agree with your assessment of the variable speed pumps, they keep running at a low level and using up 2amps. Then in the middle of a shower they decide to not work at all. In my experience an accumulator tank made no difference at all with they they worked. Iím back to the old Par 2.9 and since they arenít much more than $100 I carry a spare. An inherent advantage is that is takes five minutes to replace since the mounting holes align and the hoses have a quick connect feature.

As for the pressure switch: I took mine apart the last time it went out and found that hard water accumulation was the culprit. Unfortunately when putting it back together after cleaning I lost the little spring in the bilge so Iím not sure I fixed it. Spare pressure switches are available (but donít come with springs).

Jabsco still makes a diaphragm type freshwater pump but itís pretty expensive. They have pressure switches attached. I have two more of these as spares but the rubber is all deteriorated.
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Old 28-05-2019, 10:19   #8
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Re: Water Pump Pressure Switch

I installed a Jabsco variable speed pump about 18 months ago and had the same issue almost immediately. I chalked it up to a leaky pressure release valve on the hot water heater but when I finally got around to replacing the valve, the cycling continued.

So the question is this: Is there a high-quality marine-grade variable speed fresh water pump that doesn't have this problem?

I thought I was buying the best pump out there with the Jabsco, but silly me, reputation and cost apparently mean nothing anymore. The thought of reengineering my freshwater system with automotive relays doesn't really appeal to me as I'm from the KISS school of sailing and no longer have the brain cells to deal with complex configs.

Thanks,

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Old 28-05-2019, 10:20   #9
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Re: Water Pump Pressure Switch

The Jabsco "Par-Max" and "PAR-Max Plus" diaphragm pumps come with integral pressure switches.
About Pressurised Fresh Water Pumps ☞ https://www.jabscoshop.com/advice-an...ater-pumps.htm
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Old 28-05-2019, 11:13   #10
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Re: Water Pump Pressure Switch

Conventional pump with a good accumulator. Last replace, oh, maybe 25 years ago.
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Old 28-05-2019, 11:20   #11
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Re: Water Pump Pressure Switch

From my link in post #9.



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Old 28-05-2019, 14:21   #12
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Re: Water Pump Pressure Switch

I think what the majority are missing is that I don’t want a pump with built in pressure switch. The pressure switch seems to be what most often causes issues in fresh water systems. So I want the time proven reliability of a diaphragm pump with a replaceable pressure switch.

The Square D pressure switches I’ve looked at are around $15-$25. They come standard in 20-40, 30-50, and 40-60 psi models, and can be replaced with only a screwdriver in minutes. Seems to me to be a better alternative then dealing with replacing pumps all the time. I’ll post back when I find out which model if any is 12v compatible.
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Old 28-05-2019, 14:38   #13
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Re: Water Pump Pressure Switch

I have not heard of a simple diaphragm pump that will run 50 psi--which is most mains supply pressures where I live.

I ran a Jabsco ParMax 4 system for over five years full time use and the system was fully functional when I removed it, but I did replace the rubbish bearings with pre-packed Japanese stainless steel ones good for 10, 000 hours about three years in when the others just got too noisy.

While so doing opened the pump itself to see if it was badly worn--and removed a piece of plastic from it--these pumps need a debris filter between the tank and the pump on the low pressure side of the pump..It had not noticeably affected the working of the pump though.

If you want to fit an alternative pressure switch, that would be no problem. Just disconnect the one you imagine is the problem, but leave the wires coiled and wrapped in case the problem persists.



If your pump keeps running, I suspect there might be more to this than just the pump. An obstruction in the low pressure side such as a blocked filter might also keep the pump running.

The electronic switch models work fine without an air-reservoir accumulator, but the earlier ones which had a diaphragm and micro-switch work best with an accumulator.
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Old 28-05-2019, 14:48   #14
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Water Pump Pressure Switch

A square D switch will work, your not the first to have done it.
I havenít but have heard of it.
For me itís not the pressure switch usually, itís the microswitch that is being asked to carry way more current than it should, so I replaced the micro switch, and did the automotive relay thing so that the micro switch now only carries enough current to close the relay, and the relay runs the motor.
Funny thing is the relays donít seem to last any longer than the switch did, but they are a simple plug in replacement, the switch take 30 min or so by the time you remove and reinstall the pump etc.

I suspect the pressure switch is the microswitch that Iím describing.
Pull the number off of it, the pump manufacturer wants to sell you a complete head probably, but the micro switch can be bought on Amazon and other places for a whole lot less.
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Old 28-05-2019, 16:12   #15
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Re: Water Pump Pressure Switch

Quote:
Originally Posted by Kalimniosjohn View Post
... So I want the time proven reliability of a diaphragm pump with a replaceable pressure switch...

Jabsco Par-Max 3 Water Pressure System Pump, 12Volt, 3.5 GPM, 40 PSI Switch
Item #1 - Pressure Switch #18916-1040
$29.87 USD @ Fisheries Supply


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