Upgrading just the pump on a watermaker?

[a64pilot]

I would assume that it’s rare indeed to vary pressure by voltage.
Most use a needle valve or other means to regulate pressure with a constant speed / volume pump.

That lifespan of three years, it’s based on how many hours per day or week of operation?

[s/v Jedi]

Originally Posted by a64pilot

Then there is the quandary of why not drive up the pressure to increase output?
The membranes are good up to 1000 PSI from data I can find.

The reason you can't do that is because the membrane has a maximum product flow. I always adjust pressure to match the product flow from the spec sheet, adjusted for the feed water temperature.

I tested here in the marina where the Panama Canal outflow make the water brackish at 1,750ppm (instead of normal 26,000ppm) and I only need 500psi to reach maximum product flow (24gpm with 30 degree Celsius feed water).
If I wold crank the pressure up to 800psi, I would damage the membrane or at least shorten it's lifespan

[a64pilot]

Originally Posted by s/v Jedi

The reason you can't do that is because the membrane has a maximum product flow. I always adjust pressure to match the product flow from the spec sheet, adjusted for the feed water temperature.



I tested here in the marina where the Panama Canal outflow make the water brackish at 1,750ppm (instead of normal 26,000ppm) and I only need 500psi to reach maximum product flow (24gpm with 30 degree Celsius feed water).

If I wold crank the pressure up to 800psi, I would damage the membrane or at least shorten it's lifespan

I understand that, however most Watermakers don’t come very close to the max output of the membranes, assumption may be that one reason is so that people don’t overrate them in brackish water and damage them.
Mine for instance which is a very common Watermaker has two 40” membranes that are capable of 40 gls total output, but the Watermaker is rated to produce 30 GPH, turning up the pressure can increase the output, but of course stay below the membrane limit of 40 GPH. In any event, never exceed 40 GPH of output, cause you could in water that has a lot of fresh water in it.

[s/v Jedi]

Originally Posted by a64pilot

I understand that, however most Watermakers don’t come very close to the max output of the membranes, assumption may be that one reason is so that people don’t overrate them in brackish water and damage them.
Mine for instance which is a very common Watermaker has two 40” membranes that are capable of 40 gls total output, but the Watermaker is rated to produce 30 GPH, turning up the pressure can increase the output, but of course stay below the membrane limit of 40 GPH. In any event, never exceed 40 GPH of output, cause you could in water that has a lot of fresh water in it.

I think you have a 1hp motor on the pump? To go from 30gph to 40gph you need a 1.5hp motor and possibly a different pump. That's all, the membranes are good for 40gph but they need more water flow to get there

Rich on s/v Third Day has a Youtube video explaining this pretty well.

[a64pilot]

You would need both a larger motor and a bigger pump, a bigger motor would run at the same speed and pump no more water, just a bigger pump would overload the motor and it would shut off due to heat build up.

However, the 30 GPH Watermaker makes well more than 30 GPH, usually I believe around 35 GPH, so a bigger pump and motor to get just 5 more GPH may not be worth it, depending on how bad you want that extra 5 GPH.
Plus a Honda EU2000i can’t start the bigger pump and motor, so now your outside of the Honda’s capabilities, which is likely smart to stay within in case your built in generator has problems.

[s/v Jedi]

Originally Posted by a64pilot

You would need both a larger motor and a bigger pump, a bigger motor would run at the same speed and pump no more water, just a bigger pump would overload the motor and it would shut off due to heat build up.

However, the 30 GPH Watermaker makes well more than 30 GPH, usually I believe around 35 GPH, so a bigger pump and motor to get just 5 more GPH may not be worth it, depending on how bad you want that extra 5 GPH.
Plus a Honda EU2000i can’t start the bigger pump and motor, so now your outside of the Honda’s capabilities, which is likely smart to stay within in case your built in generator has problems.

Some pumps you can change out the cams to get a bigger stroke when connecting to a bigger motor.

My 40gph dual 2540 membrane watermaker will make 50gph here in the Caribbean so that is well more than the 35gph from the 1hp motor version. The use of a Honda 2000 is the only real reason for the 1hp motor I think because the cost difference is minimal. I don't have a Honda 2000 though and can run it from either the Northern Lights or even the inverter