Does an Irrigation System Need a Pressure Tank?

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If you’re wondering whether you need a pressure tank for your irrigation system, you’ve come to the right place. As pressure is crucial in determining the efficiency and effectiveness of your watering techniques, it’s essential to have a deeper understanding of this equipment. 

An irrigation system requires a pressure tank in areas with frequent variations in water pressure. It helps maintain constant water pressure. It also increases the pump’s lifespan by preventing the motor windings from heating up and burning out. 

In this article, I’ll explain why you need a pressure tank for your irrigation system. I’ll also talk about how to pick the best one for your needs. Read on!

Why Does an Irrigation System Need a Pressure Tank?

You want to understand why you need a pressure tank in the first place. If you already have a pump, won’t it be enough to handle the pressure requirements of your irrigation system? What if you use a low-pressure system like drip irrigation on your property?

Below, I’ll highlight two reasons explaining why an irrigation system needs a pressure tank.

1. Considerable Pressure Fluctuation

It’s normal for the water pressure in your property to fluctuate by +/- 10 psi (pounds per square inch) every day. However, if there is high water pressure (75 psi and above), it can cause a significant strain on your irrigation system.

High water pressure can be due to the water company. Changes in your land’s elevation can also contribute to the increase in water pressure.

For instance, let’s assume you have a sprinkler setup for your backyard. According to the manufacturer, the maximum operating range for the appliance is 45 psi. 

If the water pressure in your household is 45 psi but goes up to 60 psi in certain spots on your property, you’ll notice several problems.

The sprinklers affected by high pressure produce mist. This is an issue as wind can cause the droplets to drift away. There can also be higher water loss due to evaporation. 

As a result, your sprinklers won’t be able to water your property efficiently and effectively. You’ll notice an increase in your water bills. Insufficient irrigation affects plant health; high pressure will gradually damage your sprinkler system. 

Higher pressure also increases the flow rate of your sprinklers. If more water is available than the soil can absorb, water starts to accumulate. It can cause the plant to rot due to excess moisture in the ground. 

2. Pump Flow Rate Is Greater Than Pipe Flow Rate

Another situation where it makes sense to get a pressure tank for your irrigation system is when the pump’s flow rate is greater than the pipe flow rate. In other words, your pump moves more water than your pipe can handle, resulting in a bottleneck.

What can happen in this situation? If you don’t take immediate action, it will damage your pump. There’s also the chance of the motor dying over time.

Why is it bad when the flow rates are different? 

Well, your pump is designed to operate at a constant flow rate and pressure. If your pipes can’t keep up with the pump, it will cause pressure to build up.

The motor switches off when the pressure exceeds the pump’s operational capabilities. It waits until the buildup of pressure reduces before starting again.

As the change in pressure is quick, your pump will repeatedly turn on and off. This is known as cycling. 

Constant cycling is terrible for your pump as it causes the winding (a component responsible for moving water) to heat up. Because of the rapid change, the windings burn out, resulting in the motor’s early death.

How To Select a Pressure Tank for an Irrigation System?

Now that you know why an irrigation system needs a pressure tank in these cases let’s understand how to select the best one, depending on your requirements. 

1. Capacity

The pressure tank can act as a reservoir for your irrigation system, temporarily reducing the pump’s workload. It stores water and allows you to use it for irrigation without turning on the pump.

You can calculate the capacity of the pressure tank depending on the pump’s flow rate in your irrigation system. Generally, the pressure tank capacity should be at least four times that of the pump’s flow rate.

For example, if your irrigation pump has a flow rate of 15 GPM (gallons per minute), your pressure tank’s capacity should be at least 60 gallons. 

However, this isn’t the case for pumps with variable frequency drive (VFD). VFD allows the pump in your irrigation system to change its flow and pressure depending on how much water you require.

Regarding VFP pumps, you only need pressure tanks with a small capacity, around 1 to 2 gallons. Why? It’s easier for these systems to maintain constant pressure. 

2. Flow Rate & Pressure

Another factor you need to consider when selecting a pressure tank is its operating flow rate and the pump’s pressure. 

Generally, you can’t go wrong if you choose a pressure tank with a flow rate of 10 times that of the pump. However, you may have to install more pressure tanks, especially if you water a large area.

The pressure tank’s minimum pressure should equal the pressure your irrigation system needs for optimal operation. 

Make sure you account for pressure loss in the system. As water flows through the network, its pressure reduces due to friction. Also, the pressure goes down as the length of the piping increases. 

It can be challenging to pick the right pressure tank for your irrigation system. Ask a certified professional to help you decide. After evaluating the requirements for your irrigation system, they’ll recommend the best solution for you. 

Final Thoughts

Installing a pressure tank for your irrigation system is an excellent decision if the water pressure in your area fluctuates significantly. It also makes sense to go for this appliance when your pump’s flow rate is greater than that of the pipes in the network. 

When you’re choosing a pressure tank for your irrigation system, make sure you factor in capacity, flow rate, and pressure. If you can’t decide what’s best for you, a certified professional can always provide the right solutions based on your requirements. 

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