Potable water pump ?

[rainforest]

Can someone recommend a least expensive potable water pump that has a SMOOTH FLOW - not one that cycles ON / OFF / ON /OFF ...

[rslifkin]

Any of the pumps that are variable speed or have an internal bypass will be able to flow smoothly down to a pretty low flow rate.



The other option is a conventional pump with a sufficiently big pressure tank after it. Then you get a smooth flow with the pump running to charge the pressure tank and then shutting off. Water will flow with the pump off until the pressure tank is drawn down enough, then the pump will turn on to re-charge it.

[tkeithlu]

I'm not sure what you are trying to achieve. An ordinary diaphram pump with a pressure switch in theory pulses but practically delivers a smooth flow because of the elasticity of the hoses, whcih absorb the pulses. A very low flow in that situation would cause the pump to cycle on and off as it pressurizes the hoses.In that case, a pressure tank will damp it. A very short system with very little elasticity would do the same, and the same solution is possible.

A vane pump would be pretty smooth in any case, but using one to hold pressure would not work very well and might destroy the pump.

So, could you tell us more about the problem you are facing? If a pressure tank won't solve the problem, why?

[Shrew]

You need an expansion tank. That will address the short cycling of the pump. I don't suggest a variable speed pump. I had a paramax and the switch would slow way down, but not actually stop. It would then overheat and shut off. I had to shut the breaker off and on to get the pump working. I gave up and replaced it with a fixed speed pump and an expansion tank.

[rainforest]

THANKS ......... that's the reply I needed. But now to figure out where i can fit an expansion tank. CHEERS !!!

[rslifkin]

As far as fitting the expansion tank, it doesn't necessarily need to fit right near the pump. As long as it's plumbed into the cold water line coming from the pump and there aren't any check valves in between, it can go pretty much anywhere in the boat.

[desdestiny]

Rainforest
I have a solution to the water pump issue.
Please contact me on des@edgetec.net for more details

[desdestiny]

BTW
An expansion tank does not solve the problem - it merely extends the cycle time of the ON/OFF pump cycling. The larger the expansion tank, the longer the cycle time. On boats where space is limited - it is not possible to fit a suitably sized expansion tank.

[Rumrace]

Accumulator. Add one and the pump will love you portable or fixed.
My thoughts
Cheap portable Princess Auto has boxes of them

[Rumrace]

The accumulator can be tiny. A small boat with one sink a pint would be fine.

[skipmac]

Originally Posted by desdestiny

Rainforest
I have a solution to the water pump issue.
Please contact me on des@edgetec.net for more details

I would be interested as well. Any reason you can't post the solution for all to see?

[Scubaseas]

..... but practically delivers a smooth flow because of the elasticity of the hoses, whcih absorb the pulses....?[/QUOTE]

Sorry but hoses are not this soft. Any hose rated to handle 40psi does not have anything near this kind of elasticity. You need to install an accumulator tank. It can be anywhere on a cold water pipe assuming there are no check valves upstream of it. Bigger the tank the better. These work very well with cheapy diaphram pumps. There will still be some variation in pressure but not very noticeable
.

[desdestiny]

Thanks guys - in the past I have been monstered by the site moderator and I am not sure of the rules - however I built a pressure controller to solve the problem - it is designed as an after market retro fit to a standard mechanical switched pump.
I had one of the variable speed pumps which failed and I pulled it apart to find out why.
I then built a PWM DC motor controller controlled from a microcomputer using an industrial grade pressure sensor. The low cost pressure sensor used in the current pumps is the cause of failure.
I have a detailed explanation document which I am happy to share with anyone and a youtube video which shows the system performing..

[desdestiny]

For youtube video see

https://www.youtube.com/watch?v=z96FgUBhzNQ

[jpstevens]

We have a Shurflo Aqua King II, 3.0gpm. It supplies a strong, steady flow, but I am going to install a Shurflo accumulator ($46.00 on Amazon or $36.00 for a generic twin) to save wear on the pressure switch. Wife is very happy with it.