Pump head pressure charts - determining the correct water turnover

[Alexander1312]

I am trying to find the right DC return pump for the flow I am looking for.

Many return pumps have charts like the one attached, and I am trying to confirm my understanding of how to read these chart.

The way I am reading the one attached shows that at a height of 3.2 feet, the max flow is only 792 gph vs 1050 gph, which would be roughly 75%, meaning it loses 25% of its power at this height.

So for this pump, if I set the DC controller to 5/5, I am only getting 75% of the max flow through the sump. However, I assume this will be further reduced by the fact that the pipes do not go up a straight line from the pump. What would be a realistic percentage this would further reduce the max flow?

 

[dangalang]

It won't let me copy and paste for some reason, but there is a section on loss of flow in this article: https://www.reefaquarium.com/2012/aquarium-plumbing-basics/

 

[richiev]

From a theoretical physics standpoint, I think all that matters is height, not horizontal distance. The energy required being based on the difference in potential energy between a mass at height=0 to height=SomethingBigger. From a practical standpoint the horizontal run does matter, due to friction losses during movement (water hitting the edge of the pipe, any vortices generated, any snails in the way, particles of hair algae or scum, ...).

Additionally there's no guarantee that if the calculated flow rate is 792 gph, that at 50% power the flow rate is 792 * 50% = 396 gph. The pump might be more efficient at certain ranges, the friction trade offs might be different, ...

The real answer is get one that's not too big and not too small and if you care, either a flow meter or a 5 gallon bucket + a stop watch.

 

[JVU]

You are reading the chart correctly.

As a general rule:
1 foot of vertical rise = 1 foot of pressure
10 feet of horizontal run = 1 foot of pressure
1 90-degree bend = 1 foot of pressure

Add them all up and you have your head pressure. Use the chart for your specific pump. Different pumps have different head pressure/flow functions depending on design so using one pump’s chart for another pump can be way off.

The horizontal run and 90-deg parts are estimates based on the resistance in common pipe sizes and flow amounts. The smaller the pipe or faster the flow, the more head pressure they will give.

Then use the chart for the specific pump and you will have your theoretical maximum flow. Real flow will likely be less. And may well decrease over time if junk builds up for example.

 

[Fish Boss]

You are reading the chart correctly.

As a general rule:
1 foot of vertical rise = 1 foot of pressure
10 feet of horizontal run = 1 foot of pressure
1 90-degree bend = 1 foot of pressure

Add them all up and you have your head pressure. Use the chart for your specific pump. Different pumps have different head pressure/flow functions depending on design so using one pump’s chart for another pump can be way off.

The horizontal run and 90-deg parts are estimates based on the resistance in common pipe sizes and flow amounts. The smaller the pipe or faster the flow, the more head pressure they will give.

Then use the chart for the specific pump and you will have your theoretical maximum flow. Real flow will likely be less. And may well decrease over time if junk builds up for example.

Just to add to this, it would seem like (at least in my mind) that using 2 45 degree bends would result in less loss of head pressure due to not as sharp sudden turns in plumbing, but this is not true. 2 45s still result in 1 ft of head pressure. So if you can utilize 2 45s rather than 2 90s to get stuff lined up, thats better, but using 2 45s to “soften” the bend has the same result as just using a 90.

As far as a pump goes, since dc pumps are controllable, I like the idea of getting an oversized pump, and running it at a lower rate (should last longer, more wiggle room on calculations, can add more reactors later on, etc) rather than getting a perfectly sized dc pump.

 

[Alexander1312]

You are reading the chart correctly.

As a general rule:
1 foot of vertical rise = 1 foot of pressure
10 feet of horizontal run = 1 foot of pressure
1 90-degree bend = 1 foot of pressure

Add them all up and you have your head pressure. Use the chart for your specific pump. Different pumps have different head pressure/flow functions depending on design so using one pump’s chart for another pump can be way off.

The horizontal run and 90-deg parts are estimates based on the resistance in common pipe sizes and flow amounts. The smaller the pipe or faster the flow, the more head pressure they will give.

Then use the chart for the specific pump and you will have your theoretical maximum flow. Real flow will likely be less. And may well decrease over time if junk builds up for example.

Very helpful John. This was exactly what I was looking for. Thank you.