Learned something new

well I learned something today that has to do with pumps. most of you know I am having troubles dialing in my bullet 2 and I contacted P/M and after a few questions back and forth I think we figured it out. Just because you have a pump that will flow a lot of water per hour does not mean that it will have the required head pressure to power the object you wish it to.

now I know I should have done more research on pumps before I got my reeflo dart but I was looking for a pump that would have the gph to flow my skimmer, reactors, and return for the tank. I thought that the dart would handle all that because the gph was higher then I would require and by dialing back a bit on the pump I would increase the pressure it was putting out..... Guessed wrong, the dart pump when dialed back will decrease the gph but not increase the pressure. That pump is designed to be a flow pump, not a pressure pump and I skimmed over that when I placed my order. So now the good news is that I found a gen-x pcx 40 which is one of the pumps that P/M recommends on ebay for 104 with shipping. I checked P/M's website for the manual and saw this little comment.

"~While other pressure pumps may work well with your skimmer, we know these will work well.~"

so again I have learned a few things tonight and they are:
1. RTFM!!!!!!
2. Go with the recommended pump for the skimmer.
3. check to see if high flow also comes with high pressure
4. research, research, research, ask questions, ask more questions and ASK AGAIN!!!
Remember that 3reef is a great place for information and if you can not find what your looking for in the search menu ask for help in the forums

This is Matt signing off for the night with an even bigger head ache and a slightly lighter wallet..

 

Pressure and flow are two seperate things not related to each other. A pump can produce gobs of volume but little head(pressure) or vice versa produce very high head but little volume(flow).

All good aquarium pumps list the GPH (flow or volume) AND head(pressure they are capable of producing expressed in vertical feet) on the box or label. They also have a "Pump Curve" which is documentation showing where the flow and pressure intersect for a given situation. One foot of head is equal to 0.433 psi or the inverse is 1 psi is 2.31 feet of head. If you need 10 psi you need a pump that will produce at least 23 feet of head at what ever flow you require. Look at the curves and find a pump where those lines intersect at your desired flow rate or GPH.

When buying a pump first determine your needs plus a little fudge factor. Then look up the pump curves for all those pumps you think fit the bill and buy the most efficient pump you can afford that will produce the GPH and head you require. Remember, this pump is going to run 24/7/365 so look for electrical efficiency or watts consumed pre gallon pumped. Most centrifugal pumps use less watts or consume less power when you begin to add head or pressure since it also reduces GPH or flow at the same time. Power consumption is related to the work being done. Just because the label says a pump is capable or 1200 GPH and 12 feet of head and consumes 68 watts, it does not do all three at the same time. Thats 1200 GPH at 0 feet of head or basically open discharge with no lift up to the display or valves to restrict flow. At that point it is probably consuming the 68 watts. Start to add head or back pressure to the pump and two things happen, one is the flow or GPH starts to drop and the other is the watts consumed go down. At somewhere close to 12 feet vertical lift, or maybe 5 feet up to the tank with a bunch of elbows, pipe reductions an something like eductor nozzles the pump runs out of head and produces basically no water. This is called shut off head and is the point where it draws the least amount of watts since it is not moving water or doing work. You need to reach that happy medium.

High pressure pumps will almost always draw more power since the impeller and volute are designed differently than a high volume type pump. If you don't need a pressure pump I would not buy one since it will cost much more to operate long term 24/7/365. On the other hand if you need pressure they are available but you have fewer choices to choose from as you have found.

 

Nice explanation desertrat. It's great having a hydrodynamics expert here on 3reef.

K+

 

Agreed, but sometimes you just have to go through it before it sinks in. Thank you for your info it helped, and will continue to help