Water pumps

Russ Calasant

Active Member
Dec 9, 2009
2,128
East Greenwich, RI
Boat Info
2001 480 DB
Engines
CAT 3196
Anyone understand how a dual pump freshwater system functions? I had good tap pressure at one time, had to replace a faulty pressure switch on one of the pumps and it’s been weak ever since. I’m thinking it has to do with the adjustments. Are both the pumps suppose to run simultaneously ? I can’t find anything that really explains how both pumps are supposed to work together nor how to adjust and set up the system. Thanks-
 
Russ, I had to replace the diaphragm in mine. Defender sells rebuild kits that include all the parts.
 
Russ, I had to replace the diaphragm in mine. Defender sells rebuild kits that include all the parts.
Hey Brian, pumps are good. They don’t run together, not sure if they are supposed to and want to understand the design and optimum performance - how they are supposed to work
 
The dual pumps are in the bigger boats because of the increased demand. You should hear 1 pump come on and if it cannot keep up they will both run. In a perfect world they would run together but that’s not reality. You can pretty much run 1 or 2 sources with only a single pump but beyond that you will need both to keep constant pressure.
 
On my 460. I have replaced both pumps.
Now pump #1 is running continuously.

The old pumps did the same thing but it was pump #2 that ran all the time.

Thoughts?
 
On my 460. I have replaced both pumps.
Now pump #1 is running continuously.

The old pumps did the same thing but it was pump #2 that ran all the time.

Thoughts?

I had one pump that started running continuously, I turned off both and cleaned out the filters at the head of the pumps. I reassembled and purged air at all faucets. This solved my problem, your results may vary...
 
If a pump is running continuous then it typically is sucking air somewhere. I will admit that I replace both of mine with the 4gpm shurflo and have been very happy the past 2 years. Let’s be honest, the plastic strainers and connections on these pumps are crap so it’s really not surprising we all have issues.
 
I’m just trying to figure out how the pressure switches are supposed to be adjusted. It seems that only one pump runs. Are they supposed to run together? And if only when demand increases how do you adjust properly so that occurs per design?
 

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