Prospecting Water Pumps – Some Basic Thoughts

Written by DOC

We get a lot of “pump” questions, so I figured I’d grab some posts from the last year and put them into this post.

Here is our “small pump” storage room.

Some Q&A

You state in your video that a Semi-Trash pump will not work for dredging. Is this because of the PSI? The HydroForce Nozzles require 40psi. I then realized that some of the Trash Pumps only have 38psi. I wish you had a link under the “pump section” on all of your Highbankers of the recommended Pump that will work for dredging also with your Highbankers.

There are really two types of pumps for prospectors.
Semi trash pumps and high pressure pumps.
Semi trash pumps will move large amounts of water with not too much PSI. Most 2″ and 3” semi trash pumps are rated about 35 – 42 psi. Rocks, sand and gravel, up to about 1/4″ – 1/2″ can pass through these based on the pump.

We like the Champion 2″ as far as “cheap pumps” go.  it comes with just about everything you need to get “started”. But you’ll probably replace some of what it comes with.

High pressure pumps have different “water moving” parts with tighter tolerances. (for lack of a better word) This gives them higher pressure. On a 2″ it might range from 70 – 95 PSI. Often the GPH is about the same.

If you are dredging…. you always want to overpower your unit with psi. This will allow you to run your engine less than full throttle and still have REALLY good suction. We have run our mini (1.5″ dredge) with the same high pressure pump as our 4″ dredges. We simply let the motor run just above idle. Running a 2″ then move the throttle up more. Running a 3″ more… etc. GPH is usually not the key issue with pumps and dredges. Most high-pressure pumps have good gph.

The Northern Tool Northstar 2″ high pressure pump is a GREAT pump to use for dredging.


If you let gravels and large sands into the pump you will have to open up the impeller and clean them out. The pump will stop working. Put a fine screen that uses 1/8″ mesh (or smaller) around the pump.

Now the questions is…….. can I use a high pressure pump on my unit as a highbanker?

Yes, usually with no problem…. but it can be hard to control the GPH on a high pressure pump. (Because it is is high pressure.)  If you do…. reduce the flow at the PUMP with a ball valve or gate valve.

PSI needed for GOOD dredging?

These are “minimum ball parks” for good performance.

Remember… we have used a 90 psi pump on a 1.5″ dredge nozzle.
ALWAYS go higher than you might need.

1.5″ …… 40 psi.

2″ ……… 50 – 60 psi.
2.5″ ……. 50 – 70 psi

3″ ……… 80 psi

4″ ………. 80+ psi

5″………. We like to run dual 2″ pumps that are rated at 90 PSI.
Note: We only have to run them at about 50% rpm for great suction.
This is on a DUAL hose jet log.
6″………. Same as above but pumps run at 100% RPM.
Or run the 3″ high pressure pumps necked down to 2″.
When you do this, the RPM can be 50% due to the increase
in GPH and PSI.


Also here is a head lift to PSI conversion tool

Can I reduce a pump, I was told it was bad for it?

It REALLY frustrates me when I hear people being told that reducing a pump will “burn it out”. NOT TRUE.

Reducing a pump…

Shown below is what I use to reduce 2″ semi-trash pumps to 1.5″ hoses.
We also use the same setup to reduce 3″ pumps to 2″
Reducing at the pump saves money on hose and bulk.
Also…. before you glue it up, MAKE SURE the handle clears the “roll cage” around the pump.
Otherwise you won’t be able to screw it on. Yes, guilty as charged.
ALSO…. reducing the pump OUTFLOW will NOT damage the pump. 

If someone has told you this… send them this article.
It’s not that they’re stupid… they are just passing down a MYTH.

“Most engineers falsely believe that the RPM of a pump must be reduced for the power required to also be reduced. This is simply not true when you are talking about pumps with centrifugal impellers. With these type pumps the excess backpressure (created by choking a pump with a valve) is a free by product of horsepower. As the pump pressure increases, the weight of the water being lifted is reduced and the power required decreases. With centrifugal impellers, restricting the flow rate with a valve reduces the power required proportionally. When pumping fairly cool water, these type pumps can be choked back to very small flow rates without any harm to the pump or motor. It is easy to tell if an engineer or pump installer truly understands what they are talking about if he or she understands this counter intuitive property of centrifugal pumps.”
It is actually GOOD for a pump.

How far or how much hose can I use?

If you are even asking that question… I would go with a high-pressure pump. If you’re ever going to need a LOT of hose or a lot of lift, get a high pressure pump. Good example would be working beaches where with the tides, you may end up running 200 feet of hose.

You end up losing gph and pressure the more resistance you have from hose length and lift.

Should I buy a GOOD quality pump or get a cheap one?

I really can’t answer that question for you but will give you these thoughts.

Most high-pressure pumps are in the “expensive” range, so cheap is not an option really.

If I’m going “prospecting”, I prefer to bring two cheap pumps. It gives me a backup. If one fails I grab the other and my trip is not ruined. Theory there is I can buy two cheap pumps for the price a “good one”.

If I’m “mining”, like running a pump in one place 8 hours a day, 5 days a week, I want a quality engine and pump. I’m a Honda fan on water pump engines.

Any tips on pumps?

Yes, at the end of the trip or end of the season, shut off the gas line and let the pump run until the gas drains from the lines and the pump quits. Always store with a fuel stabilizer made for storage.

Change your oil every season or every 40 – 80 hours of run time. The hotter it is the more often we change it.

Always have an extra pull cord around. The best pump in the world can’t run without it.