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The Best Pumps for Your GRAF System

Posted by Callum Vallance-Poole

Are you confused about which water pump to use for your GRAF system? With a wide variety of options available, we can help you choose the best pump for your system. With different pumps come different price points. First, there are economical pumps (transfer pumps) that are less expensive but less convenient to use. Then there are higher-end (on demand) pumps that are more expensive but convenient to use. Read on to find out which is best for you and your home. 

Why Is Pumping Water Necessary?

The Water Pump acts as the heart of the engine, pumping much-needed liquid through to the engine to help it run efficiently and reliably.

Types Of Pumps

Within the supply of the GRAF systems, various pump options can be offered. 

Submersible Pump – With the submersible pump systems, we offer an automatic submersible pump with dry run protection and an automatic restart timer. If the underground tank runs out of rainwater, the tank will therefore protect itself from any further damage by running when there is no water. It will then attempt to restart itself after some time in the case that the tank has been refilled with rainwater in that time through a rainfall event. A benefit of submersible pumps is that some of them come with a water level indicator that will automatically shut the pump off when the water gets too low. One other factor is that they are hidden from sight.

On Demand Pump – This type of pump pressurises the water to the rainwater harvesting system as they are always pressurised. They have built-in sensors that detect when the pressure drops, and the pump will kick in to work automatically. If you want a pump that is on all the time and you don’t have to worry about messing with an electrical outlet by flipping the switch, this may be the best option for you.

Above-ground Pump – We also supply an above-ground pump, which comes on a wall-mounted pump console. These systems primarily work on rainwater and via the use of a float switch, which determines the level of water in the underground tank will automatically switch over to a mains water supply. The mains water will run through the pump until the rainwater level in the outside tank increases again, in which the system will automatically revert to rainwater mode. External pumps will be located outside of the tank (likely near the electrical outlet). With an external pump you will have to hide it in a hole or under a cover if you are concerned about looks.

Transfer Pump – This type of pump, you plug in when you need to use it and it then pressurizes the water. But you can’t leave these pumps to run constantly. For example, if you are using a hose nozzle with these pumps, you cannot stop the flow of water and let the pump keep running. The pump must have water going through it while it is running, or it will overheat!

In summary, ideally use submersible pumps for underground tanks, especially where the tank is some distance from the building or is very deep in the ground. Use surface pumps for tanks that are at ground level or where the tank is at risk of freezing. A surface pump can also be used for an underground tank provided the pump is of the self-priming type and the tank is not too far away.

One other point of note is that some systems on larger houses and commercial buildings can use both types; with a submersible pump pumping water to an intermediate point then pumped again to final destinations.

Flow Rate, Pressure, and Electricity

It’s important to know what flow rate and pressure your system will require, as well as what electrical power you have available in your home for use (some types of pumps require higher voltage). 

To determine what your flow rate will be, you will need to think about what you will be using your rainwater harvesting system for. For example, a toilet will require approx. 1.6 gallons per flush whereas a garden hose will require approx. 2-4 gallons per minute. Work oyt a rough estimate by adding all of these figures together to get your flow rate.

When considering pressure of your rainwater harvesting system, you will need to take into account where your pump is located and how your system is set up. If you are pumping from underground to a few floors above ground, it will need more pressure than a standard “ground level” system. Once you have considered these three factors, it’ll help with deciding the type of pump you will need!

Six Top Tips 

  • Know your budget 
  • Decide whether you want a transfer pump or an on-demand pump
  • Decide if you want a submergible or an external pump
  • Consider what flow rate you will need
  • Consider how much pressure you need
  • Take note of what electrical power you have available
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