Fresh water pressure pump - gear vs triplex diaphragm

[nfbr]

A mates Outremer cat came with an unusal fresh water gear pressure pump with external switch and check valve.

Similar to this
https://www.mareshop.eu/ms_rw_en/mar...2-24v-16466015

Any comments on gear pumps vs normal triplex / quad pumps for fresh water pressure?

[Bowdrie]

What the typical tri/quad pumps give you is the freedom from the whole works depending upon a shaft seal to prevent not only failure of the pump but the ruination of the motor.
Shaft seal=cheapest part to buy, hardest part to change.
With the "water side" segregated on the other side of a diaphragm there is never any stress against a seal.
Gear pumps are totally dependent upon a shaft seal to stay alive, and they require close tolerances of all moving parts for efficient operation, not to mention that the "innards" are fussier to rebuild/repair/change out.
The upside? they have less pulsation in their delivery, but that's of no concern if one has an accumulator tank, (recommended,) in the system.

[SailingHarmonie]

Marco pumps are excellent pumps, and in my experience they are much longer lasting than the multiport diaphragm pumps for people like us who are on our boats 24/7/365. I have used them for years, in many applications, and have been very happy.

In industrial setting gear pumps are very common, and widely used. I worked on many of them as an engineering intern many moons ago. Multiport diaphragm pumps--not so much. They are cheap. That's their primary advantage.

Yes, every two years I change the shaft seal. Takes 30 minutes. If you ignore them, after maybe 5 years the shaft seal will fail and flood the motor. A shaft sail is about $1. If you are up to doing preventative maintenance, get a Marco. If you prefer to let things run until they break and need replacing then get something cheaper--and buy two.

Taking care of things is a darn sight better--for me--than carrying a spare pump which I was always needing with diaphragm pumps to maintain the reliability we needed for sailing in remote areas. Others, apparently, feel differently.

As far as the actual performance at the tap, if the pump works, the user will never know what kind of pump is pushing the water around. Except, the Marco pump is quieter than most others.

[Bowdrie]

Originally Posted by SailingHarmonie

Marco pumps are excellent pumps, and in my experience they are much longer lasting than the multiport diaphragm pumps for people like us who are on our boats 24/7/365.
Yes, every two years I change the shaft seal.

Yeah, the Marco pumps get good press.
Lifespan of diaphragm pumps?
The original Flojet pump now has almost 31 years of 24/7 service.
Perhaps I just got an exceptional one, but they tend to outlast the Jabsco and Shurflo units easily.
Proper installation always gives better pump life, (flooded inlet, no lifting of water).

[CaptTom]

I've been looking at gear pumps because I could never manage to quiet my diaphragm pumps down. I tried mounting them on a floating mount made of rubber hoses, suspending them from overhead, whatever. Apparently the plumbing carries the pulses everywhere, and they resonate throughout the hull. Personally I'm OK with that, but many find it jarring.

I'm tired of not being able to wash my hands when anyone else is sleeping!