Off-grid living highly values using natural and readily available resources. The most abundant of which being rainwater. Hawaii, being a tropical climate, has its fair share of precipitation across the year, a valuable resource ready to be harnessed!
Setting up a rainwater tank can be relatively simple. The technicalities of pumps and other mechanical components are usually what is intimidating to those looking into collecting rainwater. But do you even need a pump for a rainwater tank?
A rainwater tank located in a strategic spot to take advantage of gravity does not need a supplemental pump for most garden situations. Every 2.31 feet of water height gives you 1 psi of pressure. Depending on your needs, this may be enough pressure or you may need to add a pump.
If you are using your rainwater tank for outdoor and garden use, you likely do not need to use a pump, gravity can do all the hard work for you!
In this article, we will share how to use gravity to shift your harvested rainwater, discuss when a pump may be best suited and go over some of the most popular pumps for rainwater tanks.
Using Gravity To Move Your Harvested Rainwater
Gravity is a natural resource in itself! The use of gravity can help you move your harvested rainwater from the tank across your garden. Using gravity will also save on your energy usage and ensure your water continues to flow in the event of power loss.
Understanding how to set up a gravity-fueled rainwater tank involves an understanding of basic physics. Your tank needs to be higher than the place your water is going to allow the force of gravity to move it. If the tank is on equal ground to the destination of the water, you will get very little pressure. If your tank is below the destination, you will not be able to shift it without a pump.
If your property has a natural gradient, you can place your tank on the higher end and use this natural incline to shift the water. Keep in mind that your tank should be close enough to run a collection pipe from the guttering that will be collecting the water.
If you aren’t able to use a natural height advantage, you can elevate your tank to create the distance needed to use the forces of gravity. Your tank stand should be robust, structurally sound and completely secured to the ground. Check your local regulations as above a certain height may require a building permit.
The higher your tank is, the higher the pressure you will achieve at your outlets. To calculate your expected pressure (measured in psi: pounds per square inch) use this formula that we previously mentioned:
For every 2.31’ of height = 1psi.
The average faucet in the home runs at about 40-60psi to put that in perspective. If you want to use your pump-less water tank for an efficient drip tube irrigation system in your garden, you will need to achieve a pressure of approximately 25 psi.
When a Pump Might Be Better To Use With Your Water Tanks
Although using gravity can be efficient and energy saving for certain uses, there are times in which a pump may suit your needs better.
A pump will likely be required if your tank is a significant distance away from your home or garden as the water pressure will decrease over distance. If too far away you may not achieve a usable pressure with gravity alone.
If you want your rainwater tank to service more than just the garden for water for use in your home buildings you will need to ensure the water can travel through the home at a reasonable pressure, particularly as there can be multiple outlets requiring water at once. This is also the case if you have a multistory building, if you use gravity in this situation, the water may not have enough gravity-driven force to reach upper levels.
If your rainwater tank is underground or at ground level, a pump is needed as gravity is not at play in these situations. This may be the case if you already have a tank in place you want to use for rainwater.
A tank may be required to be installed underground level due to space or cosmetic reasons, in this case a pump is needed to shift that water from the lower elevation.
3 Of The Best Pumps For Rainwater Tanks
If you’ve done your research and surveyed your property and have decided that gravity is not going to be able to deliver your water for your needs, the next step is deciding on a pump to use. Without much knowledge in this area, it can be hard to know where to start. Here are some popular, tried and tested brands:
The flojet’s design includes mounts that are soft, designed to take on the vibration and noise emitted to reduce the sound and feel of the pump working.
Flojet also has a self-priming feature, meaning if your tank runs dry your pump is protected and won’t be damaged by trying to pull water that is not there.
These pumps are designed to work on demand, so no pressure tank is needed. Just install the pump somewhere on the outlet of your water tank, turn on the faucet and the pump will kick right on and begin to pressurize your water.
I have been using a Flojet pump on my water catchment system for over 20 years. It is a good pump, but does break down after 2 to 3 years of use so having a backup on hand is a smart thing to do.
Shurflo is valued for its low noise emitting qualities, so much so that is popular in RV uses.
Shurflo pumps also have thermal protection technologies that are designed to protect them from overheating. If your pump is going to be working overtime, it will be protected from this potential problem.
These pumps are designed to reduce internal friction, which has worked well as many reviews say they are dependable and have a long life – meaning minimal maintenance!
The pump’s unique design has no moving parts travelling more than 1/8″; this greatly reduces friction and wear and tear, which means greater dependability and longer life.
It has recently been recommended to me to switch to a Shurflo pump over the Flojet pump except they are not readily available where I live. With the cost significantly lower than the Flojet Pump and the reliability rating higher, a Shurflo pump is going to be the next pump I try out when my current pump goes out.
Grundfos is a company that creates pumps of all sizes, from the tiniest garden tank to full-on large-scale agricultural systems. If this technology can service thousands of acres of agricultural land, it should prove to be useful and dependable for your homestead.
These pumps are the gold standard when it comes to pumps and their price reflects it. However, people have told me that they love their Grundfos. People experienced with these pumps have found them to last up to 5 years! That is ancient in the pump world.
Out of these 3, from the reports getting back to me from people who actually use these pumps, the Shurflo pump would be the pump of choice for those with a lower budget, but if you can spring for the initial price of a Grundfos pump, their longevity actually brings the price in lower than the other 2 on this list. The choice is yours.