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Proper Pump and
Plumbing Sizing for Successful Installation

Choosing The Right Pump:
 Maximize Longevity,
Cut Operating Costs

4 Easy Steps to the Perfect Pump

1. Find GPH by width and appearance of falls

2. Size Tubing to provide best possible flow

3. Find the Total Dynamic Head of feature

4. Choose the perfect pump… or pumps!

how to know how much flow?

First determine total width of spillway(s)

then choose the appearance desired:

Trickle, ¼”-½” depth of water over spillway, allow 50 GPH for each inch of width of spillway 

Sheet, ½”-¾”, allow 100 GPH for each inch of width of spillway

NIAGARA, 1”-1¼” deep over weir, allow 200 GPH for each inch of width of spillway

16” weir at low flow: 16” x 100 = 1600gph
30” waterfall, high flow: 30” x 200 = 6000gph

so what’s this about Tubing Size?
does it really make a difference?

It makes ALL the difference!

Restrictive Plumbing

pond pump restrictive plumbing

but what does “restrictive” really mean?

eliminate damaging “water hammer”

reduce stress fatigue in pipe and fittings

lessen workload of pump and

Minimize flow losses due to friction so, less friction means lower head and greater water flow per watt

but, is it really all about  the size of your hose?

ok, imagine this…

pond pump flow rate pipe

flow rate experiment

just how much was that?
@ 3600sec/h x Xgal/Ysec

Filling the 10 Gallon Bucket in…

30 seconds =   1200gph       

15 seconds  2400gph

8 seconds   =   4500gph

6 seconds   =   6000gph

Circumference versus volume
versus πr2

cross section of pipe

The surface area of the small circle is 2π ; the larger is 4 π, twice as much surface area, so we might expect about double the friction in the larger circle.

The volume of the smaller circle is π ; the volume of the larger 4π, four times as much volume, so we can expect quadruple the flow through the larger pipe, with only double the friction.  The larger the pipe, the greater the difference.

Pipe & Hose Sizing Chart

To minimize friction and maximize flow and longevity

 pipe diamter hose chart

Then, Choose the perfect pump…or pumps!

following Pipe & Hose Sizing Guidelines*

Add 1 foot of head for each 25’ of hose;

Add 1 foot for every check valve;

Add ½ foot of head for every other fitting;

Add to Static Head. Round up for THD.

friction loss chart

Total Dynamic Head =

Static Head+[(Run+Fittings)/100 x Friction Loss

For a 4’ high x 30” waterfall,

find the Total Dynamic Head, with:

6000 gph through 25’ of 3” flex (chart)

1 - 90° elbow

1 - male/female adapter (bottom right table)

1 - swing check valve

4 + [(25 + 11.1 + 6.5 + 27.1) /100 x 2.66] = 6 TDH

So what? Do tubing size and head really make a difference? YES!

4’ high x 30” waterfall, 6000 gph, 25’ of flex PVC, 90° elbow, male/female adapter, check valve:

3”        4’+ [(25 + 11.1 + 6.5 + 27.1) /100 x 2.66]            =  6’ TDH

2”        4’+ [(25 + 8.6 + 4.5 + 19.1) /100 x 19.12]            = 15’TDH

4’ high x 30” waterfall, 3000 gph, 25’ of flex PVC, 90° elbow, male/female adapter, check valve:

2”        4’+ [(25 + 8.6 + 4.5 + 19.1) /100 x 5.31]            =   7’ TDH

1½”     4’+ [(25 + 7.5 + 3.5 +15.2) /100 x 21.52]            = 11’ TDH

1¼”     4’+ [(25 + 6.7 + 2.8 + 13.1) /100 x 52.41]            = 25’ TDH

and the difference is?

4’ high x 30” waterfall, 6000 gph, 25’ of flex hose, 90° elbow, male/female adapter, check valve:

pump flow rates

* Need to raise back pressure w/valve to 11’ head

pump flow rates

Tech Talk - Suction Cavitation
or, How to Kill a High Head Pump

Pondwater contains dissolved air, just like champagne contains dissolved CO2 

Drop the pressure – pop the cork – and the

            gas comes out of suspension, creating foam

Likewise, low pressure at the inlet of a high head pump operated below its minimum head draws air bubbles out of the pondwater and into the volute

The bubbles IMPLODE under high pressure at the pump’s outlet, damaging volute and impeller

The motor, spinning the impeller in froth instead of a solid column of water, overspeeds and burns out

Choose the perfect pump… or pumps!

Choose the type of pump that provides the desired flow in GPH Through the optimal tubing size at the correct Total Dynamic Head for the least wattage consumed.

so, what types of pumps are there?

Choosing the Right Pump
Direct, Hybrid, Mag, Axial

Direct Drive -- costly to run, only necessary for high head.

MagDrive -- small, simple, one moving part, easy maintenance

Asynchronous -- for high volume, low head, v. low watts

Axial Flow – DOUBLE the flow for same wattage, v. low head

Submersible Pump Applications

•Axial Flow – Very Low Head – to 9’ TDH, 0-3 psi
Pro-Very Efficient, High Volume, No Cavitation
Con-Limited Application, Requires Large Tubing

•MagDrive – Low to Med. Head – to 12’ TDH, 5 psi
Pro-Efficient, Dependable, Simple, Replaceable Impeller
Con-Bidirectional, inefficient impeller, magnet size, noise

•HY-Drive – Medium Head – to 24’ TDH, 10 psi
Pro-Asynchronous, Very Efficient, Dependable, Very Quiet
Con-Non Replaceable Impeller, flows drop off at high head

•Direct Drive – Medium to High Head – to 50’+, 15 psi+
Pro-Asynchronous, Efficient Impeller, Great Head/Pressure
Con-Seals, High Power Consumption, Heavy

you’ll want the lowest head pump possible.

 why? $$$

The Laws of Affinity state (more or less) that:

you SQUARE the power to double the Volume;

you CUBE the power to double the Pressure!

  2 times the Volume = 22 = 4 times the Wattage

2 times the Pressure = 23 = 8 times the Wattage

So, Cut the Volume, really drop the wattage

Cut the Pressure, REALLY drop the wattage

to cut the volume, how about using
 2 small pumps?

2 pump operation versus 1

does a few $ a month
really make a difference?

2 pumps versus 1

but wait – there’s more!

Advantages of Redundancy

                                    in ADDITION to the savings ???

 •Less chance of night circulation failure

•Removal for servicing/repair

•Alternating use to save wear

•Elective flow at night/ for parties/ vacations/ off season/ off hours

so, is it worth…
figuring the GPH by appearance;
calculating the Total Dynamic Head;
selecting low head, high efficiency pumps;
buying two pumps and twice the plumbing?

Bet your Bottom Dollar!


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