Estimate flow rate by head pressure

[ReefBeta]

From what I found, the rule of thumb for calculating head pressure from plumbing is 1 foot per 90 degree, and per 10 feet pipe length.

My return pump has max head of 14 ft. I have 11 elbow and about 9 ft pipe in the return line, plus 4 ft height difference. If that rule is right to any extend, it should get almost no flow even at max. But the reality is, it push plenty of flow at 50%.

So, is there a better way to estimate flow rate without a flow meter?

 

[Billdogg]

redirect it to a 5g bucket. Time how long it takes to fill the bucket. Do some basic math - for instance - if it takes 2 minutes to fill the bucket to the 5g mark, then it will fill 30 x 5g buckets/hour = 150gph.

For in tank flow I don't worry about the return pump - I go only on what my power heads supply. It make my head hurt less that way!

 

[Reefer Reboot]

The devil is in the details when it comes to calculating head pressure and there are a lot of details. (Bore finish, bore size, directional change, induced turbulence, distance from induced turbulence to directional change, edge sharpness, viscosity of fluid medium, blah blah blah.... the list goes on and on.) Now this may be important in a hi-tech hydraulic setup but for this hobby, what you have found is a pretty good estimation. Keeping your plumbing as large as possible will help. Best bet if you want to know exactly, like Billdogg said, take an actual measurement. but even then it will change over time due to the growth and silting of things like algae, sponges, detritus and what not.

 

[ReefBeta]

redirect it to a 5g bucket. Time how long it takes to fill the bucket. Do some basic math - for instance - if it takes 2 minutes to fill the bucket to the 5g mark, then it will fill 30 x 5g buckets/hour = 150gph.

For in tank flow I don't worry about the return pump - I go only on what my power heads supply. It make my head hurt less that way!

I just don't know how exactly will I fit a 5 gallon bucket inside the tank above water level while under return nozzle to do that test. I need the flow rate to properly set for UV. I won't really bother about the real number otherwise.

 

[Mical]

Here try this -> http://www.reefcentral.com/calc/hlc...Couplings=0&CheckValves=0&Exits=1&Entrances=1

 

[ReefBeta]

Here try this -> http://www.reefcentral.com/calc/hlc...Couplings=0&CheckValves=0&Exits=1&Entrances=1

Tried. Looks like the only thing matter is the vertical length.

 

[KStatefan]

If the head chart of the pump is accurate you could do that to get an estimate.

 

[ReefBeta]

If the head chart of the pump is accurate you could do that to get an estimate.

You mean disregard of how many fittings in the plumbing, just take the vertical difference, and apply to the head vs flow chart from the manufacturer?

 

[DCR]

The most accurate way to measure your actual head would be to create a valve tap with a tee right off the discharge of the pump and then extend clear vinyl tubing (or clear PVC) temporarily up towards your ceiling. When you open the valve the water will fill the tube up to a higher elevation than your tank. The static elevation difference between the liquid level in the tube and your sump is the head of the pump. The elevation difference between the tube and your tank level would be the frictional loss.

Technically, the total pump head also includes the velocity head which is the work it takes to accelerate the fluid from the sump (essentially zero velocity) to the velocity at the discharge port of the pump, which is non-recoverable. It is simply the square of the fluid velocity at the pump discharge (in ft/sec) divided by 64.4. You should add that to the elevation head. For most systems it might be around 1 ft of head

If you are uncomfortable with the clear tube, you can use a pressure gauge and divide the psi by 2.31to convert to feet of head, but it needs to be a really accurate pressure gauge with a large diameter dial.

 

[KStatefan]

You mean disregard of how many fittings in the plumbing, just take the vertical difference, and apply to the head vs flow chart from the manufacturer?

No. Use the pressure on your system and convert that to head feet then look at the pump charts and see how much flow that is.