Lift vs. GPH

[Cas8100]

Picking out a new small submersible pump on ebay for my DIY project...

Pump will need to provide about 10 feet of lift... Would I be better off with a higher "lift" rated pump or a higher flow rate (with reduced lift rating)?

The choice is between a 1000 L/Hr with 5M lift (23 watts) or an 500 L/Hr with 9M lift (19 watts). In my mind, the wattage of the pump should be the deciding factor. Anyone have other opinions?

 

[slief]

Lift? Are you talking about how high the pump will need to send water meaning head height? Did you also factor in friction loss which also adds to head height? All this is a consideration when factoring true head loss calculations. Every fitting, the tubing type, tubing diameter etc all adds to head loss. I point this out in case you are not aware that 10' of height doesn't mean that you will have 10' of head loss. Fittings and tubing type and size can quickly turn 10' of height into 15' or more of head loss.

At the end of the day, the decision should come down to desired flow and actual calculated head loss. The head loss will help you narrow down the pump choice based on the desired flow. The greater the head loss and flow needs will typically result increased wattage of the pump. Point being that wattage certainly shouldn't be the deciding fact. It is of course one factor but the flow needs and head loss will ultimately determine which pumps are suitable. Then you also have the question of reliability and the ultimate use of the pump. Cheap pumps from eBay don't always mean reliability so your application and the question of how critical this device is should it fail should also be a factor in your decision.

 

[Vinny Kreyling]

L/Hr means you divide those numbers by 4 & get 250 GPH & 125 GPH, not much, & a lot less @ 10 ft.
In my mind flow & reliability are what you should go by, just like Scott said.
You need to be looking @ flow charts too.

 

[Cas8100]

Thanks guys... This is just for a salt water top off system so I'll run it for maybe a few minutes a day. I'm using 1/4" OD tubing so the losses will be huge.

The cheapo pumps on ebay don't provide charts like you'd find on a nice brand named pump. I was just wondering which would push more water at 10' up...

 

[slief]

Not sure what to suggest in the way of a cheap eBay pump. I always use peristaltic pumps for ATO and the one I would suggest for your application is a Litermeter pump which isn't cheap but it's designed for what you are looking to do and already has the 1/4" output for the tubing you are planning to use. These pumps are bullet proof and will pump water around the block and back. They also will never siphon. It would be the last top off pump you will ever buy.
http://spectrapure.com/DOSING-TOP-OFF/LITERMETER-DOSING-SYSTEMS/Basic-LiterMeter-Dosing-Pump

 

[Cas8100]

Thanks!

 

[krazyk148]

Here are the submersibles i plan on using. Not expensive.
http://www.ebay.com/itm/291669264513?var=590700298250

 

[SGT_York]

FYI Lift vs flow is primarily impeller driven not wattage. Bigger pumps obviously will get more flow, but impeller/housing type is what produces the flow and it has more effect on flowrates at different head heights than wattage does.

An impeller that adds a small amount of water per turn will provide less flow at much higher pressures than a large flow impeller on the same pump. (+several other contributing factors) That pressure is what pushes the water higher, on a high volume pump the back pressure (AKA Headloss) significantly reduces the amount of water pushed on a high volume low pressure impeller.

Each pump will have a head loss chart sold with it, if it doesn't do not buy it because it's junk. Use a headloss calculator to estimate what your actual flows will be. Each angle and foot of pipe will increase the headloss due to increased friction. Pumps are designed for a specific usage, make sure you get the right one for your requirement.

Sounds complicated but if you use the calculator it becomes very simple. buy a pump with the flowrate you need at the head height you intend to use it at not the advertised flow of the pump (which is at the pump outlet in most cases or zero feet of head loss)