Facts: About Pumps

Not many people want to be involved in the mechanics of a pump because it can be too difficult to understand. But if you learn just a little it will help you understand the living, breathing ecosystem that is your pond.

Pumps and plumbing make up the circulatory system of a water feature. More important, they supply the system with necessary oxygen and keep the water circulating.

Water garden vocabulary:

GFCI (Ground Fault Circuit Interrupter) is designed to protect people and pets from severe or fatal electric shocks.

GPH – Gallons per hour. Means the gallons that the pump is circulating every hour and can be referred to as rated flow. Small to average water gardens and Koi ponds need to circulate every hour with a full exchange of the water in that hour. Larger gardens every 1 1/2 hour exchange.

GPM – Gallons per minute.

Pond Volume – The amount of water in a pond.

Formula for calculating the gallons in your pond.

  • Irregular Pond = length x width x average depth x 7.48
  • Circular Pond gallons = 3.14 x r2 x average depth x 7.48

Head Height – The height from the surface of the pond to where the water comes into the biofalls (usually at the bottom of the unit), which means the amount of elevation change a pump can take to pump water.

TDH (Total Dynamic Head) – The combination of the total height and the total run a pump has to push. Total dynamic head refers to the pressure on a pump caused by the interactions of flow rate, pipe diameter, pipe length, elevation, and pipe material.

The other contributing factor to the size pump you will need is the width of the waterfall when it enters the pond. You will need 1500 to 2000 GPH in a pump for each foot of stream width at the entry point into the pond basin. Large systems sometimes require 3000 GPH per foot especially if you want white water.

Basically, it takes all those things into account and lets you know the limitation of your pump.

Flow Rates – The amount of water moving in a given time period.

Mag Drive – Type of pump that relies on magnetic forces to drive the impeller. Pumps a smaller amount of water than direct drive pumps, but are more efficient and usually used for fountains and small basin applications.

Direct Drive – Type of pump in which a motor drives a shaft that spins the impeller. More durable than a mag drive and usually used to provide water to a waterfall.

Watts – Electrical power consumption of a motor. Watts = volts x amps

Amps – The rate of flow of an electrical current.

Check Valve – Valve that prevents water from back flushing from the BioFalls to the skimmer where the pump is located.

PVC (poly vinyl chloride) – A common thermoplastic resin.

All of the Aquascape and AquascapePro line of pumps are made specifically for water gardens. They are submersible pumps which also need to be placed in a skimmer or wet well.

Specifications can mean the difference between a gushing waterfall and a trickle that sounds merely like a leaky faucet.

Operating Cost
Look for high efficient pumps. Obviously the bigger the pump is, the larger your operating cost per month can be. High efficiency pumps use less power.

Waterfalls and Pump size
Establishing the flow rate for your pond is probably the most important thing to do when it comes to your waterfall.

Experts say that for each foot of spillway width as it enters the basin, you should allow 1500 to 2000 GPH. For example, a 2 foot waterfall width usually requires between a 3000 gph to a 4000 gph pump.

Then, there is the waterfall and stream height to factor in and the term, shut off height, comes into play. Most people believe that a pump rated at 3000 gph will always push that amount of water. But once you subject your pump to higher waterfalls or longer streams, it will push less water. Once it hits that shut off height, you are not going to get any more water.

Call us a 877-780-1174 if you have any doubt in the size pump you may need.


Plumbing used with pumps is also an important part of the equation. Using the wrong plumbing can cause friction, hindering the performance of your pump and affecting the power of your waterfall.

We believe that the Flexible PVC is the best for pond projects. It will handle sharp turns and tight corners and also expands and contracts with seasonal changes.

…1.5 inch pipe has a maximum flow rate of 2200 GPH

…2 inch pipe has a maximum fow rate of 4800 GPH

So you can see that pipe selection is very important.

Check Valve
The check valve helps prevent water from back flushing into the pond when the power to your pump is cut. The reason this is important is because you need to keep water in your biological filter so that the beneficial bacteria can continue to grow. The bacteria will die in two hours without water.

Other terms
Discharge – The opening of the pump where the water is expelled.

Impeller – The part of the pump that pushes the water. It generally has fins or blades.

Shaft – The shaft is what spins the impeller. It is generally located inside the motor housing.

Motor – The motor is what drives the pump. The shaft attaches to the motor.

Impeller Housing – This is where the impeller sits and is allowed to spin.

Now you really know how that pump works.

Planning: Sizing Your Pump!

Minimize friction losses by using large diameter pipe. Determine the approximate flow rate that you want, the head height, and the total length of pipe. Consult a Friction Loss Chart to choose the proper diameter pipe.

You can calculate your total head at www.pump-world.com. You will need to know the following:

  1. The overall height
  2. The pipe run and diameter of pipe
  3. The maximum rated flow for the pump

The size of the pump’s suction and discharge ports DO NOT dictate your proper pipe size. Choose a pipe diameter that keeps your friction loss below about 6 feet per 100 feet of pipe. The longer your run of pipe, the more critical it is to minimize your friction loss. Normally, a minimum of 2 inch line is suggested for systems with flow rates from 30 to 50 gallons per minute or 1800 to 3000 gallons per hour.

Use a filtration system that DOES NOT require a lot of pressure. It costs MONEY to create pressure. Biological filters and BIOFALLS® filters work well and require no pressure.

Pipe Diameter Max GPH
1.5 inches……………….. 2,200
2 inch……………………… 4,800
Two 2 inch pipe……….. 9,600
3 inch……………………..10,500

Remember to consider the width of your stream when it enters the pond. You will need 1500 to 2000 GPH for each foot of stream when it comes into the pond.

NEVER run a pump dry. This will damage the seal and impeller. They are designed to pump water, not air. Insure the pump is submerged in water before you turn it on, and be sure it does not out-pump the supply.

If your pump is producing too much flow, you can reduce the flow by partially closing a valve (Ball valve) on the discharge line near its outlet (NEVER RESTRICT THE INLET). Also never restrict more than a quarter turn.

If more flow is required than a single pump can produce, use two or more pumps. This also offers the benefits of being able to vary the flow rates; this can often save a substantial amount of electricity compared to using one very large pump.

Choose a pump that can give you the required flows at the lowest possible AMP draw.

If you have any further questions, please send to info@aquascapes.com


877 780-1174

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