Pump Flow rate - Will increasing pipe diameter increase flow a lot?

[IanS]

My pump is 'Blagdon 3500' which is supposed to have a flow rate of over 3000 ltr per hour.

I just tested it - number of seconds to fill a 1 ltr jug - it took 7 seconds.

By my calculation that's just over 500 ltrs per hour. Way below what the manufacturer claims.

The test was through 4 meters of half inch hoze at ground level, ie max 6 inches head. (no filter in the test, just hoze and pump and the jug) If I switch to 3/4 inch hoze will that make "much" difference?

Thanks

 

[addy1]

The larger the hose the less loss of flow due to head pressure. You will get more flow out of a larger hose, it sounds like the 1/2 inch size is restricting the flow.

 

[IanS]

Thanks Addy1.

You're right. The 1/2 inch pipe really is a a BIG restriction.

I found a handy website that does the flow rate calculation based on bore diameter, pressure, length of pipe.

Using the site calculator I can see that, with my 4 meter length, increasing from 13mm to19mm connectors and pipe will get my flow rate from 600ltrs to just over 1000 ltr per hour. But a step up to 25mm pipe will get me 2300 ltrs per hour.

So, the moral of the story, don't scrimp on pipe diameter. Even small changes in bore can make a huge difference in flow rate.

Here's that site

Flow Rate Calculator - Pressure and Diameter | Copely

Our Flow Rate Calculator will calculate the average flow rate of fluids based on the bore diameter, pressure and length of the hose.

www.copely.com

That site asks for Pressure (Bar) which I've never seen listed on pumps. But bar can be calculated by Max Head. 1 (one) meter head is equivalent to roughly 0.1bar. If your pump simply stops at, say, 2.5 meters head then the max pressure is around 0.25 bar.

That site also asks for your name and contact details. It doesn't do any check to confirm your name really isn't "Fish McKoi"

After all that though I've just ordered a new more powerful pump and set of new pipes. Even with big pipe my old pump isn't up to the task. I'll use it for a backup or skimmer or something.