Collecting rainwater for use with your home sprinkler is a fine way to reduce your water bills and your household's impact on the environment, but figuring out how to shift all that water once you've collected it can be a challenge. Whether you're providing water to a couple of cheap sprinklers on your lawn or an extensive irrigation system for vegetables and crops, you'll need a water tank pump to move water quickly and effectively.
However, there are numerous types and configurations of water tank pumps on the market, and choosing the right one for your needs can be difficult. Since a sprinkler system needs low pressure and even, reliable flow to provide optimal irrigation to your plants, you should look for a pump that can best provide these qualities.
Automatic or manual?
Automatic rainwater tank pumps are considered the norm when it comes to most rainwater collection schemes, but if you're using your rainwater purely for garden irrigation, you may want to consider saving some money and opt for a manual pump.
Unlike automatic pumps, which start pumping water when any tap connected to the system is opened, manual pumps must be turned on directly before they start pumping water. This is obviously less convenient, but manual pumps are generally significantly cheaper than automatics. Just be aware that if you choose a manual pump, turning off the pump is the only way to stop the flow -- closing the tap or hose you are using will simply cause water to back up into the pump, potentially causing serious damage.
If you have a larger sprinkler system covering a wider area, you may find the extra investment of an automatic pump worth it. If you do opt for an automatic pump, make sure to choose one with a run-dry switch -- this will automatically turn off the pump when your tank is empty and prevent heat and friction damage caused by dry running.
Surface or submerged?
You will also need to choose where the pump is located within your rainwater tank -- should it be a surface or submersible pump?
Submersible pumps are the best option for people wishing to build a low maintenance, 'fit and forget' pumping system for their sprinklers. Submersible pumps are fixed to the bottom of your tank and become submerged as the tank fills. Resting at the bottom of the tank in this way ensures more even water pressure and minimises the dangers of running the pump with little or no water in the tank (most commercially available submersible pumps are also fitted with run-dry switches for added protection). However, their awkward position means that direct inspection of the pump is difficult, and if it fails entirely, you may need to call in professional help to have it repaired or replaced, particularly with larger tanks.
Surface pumps, on the other hand, remain level with the surface of the water in the tank. This positioning makes them much easier to repair and replace as needed, and since you can simply open the tank to inspect the pump, most come with built-in meters and readouts so you can directly monitor the functioning of your pump. Since a surface pump is only partially submerged, it is also less vulnerable to corrosion and clogging. However, surface pumps are generally more expensive, and since they cannot rely on gravity to provide a portion of their pumping power, water pressure can be inconsistent.