Your Drip Irrigation System Needs Help

Q. I've been using adjustable  drip emitters and replacing them every year because they plug from the hard water. They sputter air or just don’t emit water when they start a watering cycle.  When I find one like that, I open up the watering rate until a steady flow is achieved, but it doesn’t seem to last.

A. Sounds like several possible problems going on with your drip system. Let’s start with the easy ones first. Make sure your drip irrigation system has a filter installed to prevent drip emitters from plugging and a pressure regulator to prevent high water pressure from damaging the emitters.

A pressure regulator (black and white on the left) and a screen filter canister (right) together inside an irrigation box. Arrows on them indicate the direction water should flow when installing them. 

            A removable flush cap must be on each of the irrigation lines so that the system can be “flushed” on a regular basis. This helps to prevent emitters from plugging. I will talk more about this in a minute.

Some flush caps unscrew to release water. 

            The most popular filter for residential use is the inexpensive screen filter. It is oftentimes a black canister installed close to the irrigation valve used for drip irrigation. It is normally installed immediately downstream of the valve in the same irrigation box.

            The screen inside the filter should be removed regularly and gently cleaned or replaced if damaged. Clean the filter two or three times a year when using city water, more often if you’re using well water. The dirtier the water, the more often the filter needs to be cleaned.

Pressure regulators come in different static pressures and there are adjustable ones if you aren't sure of the pressure needed or it varies.

            Pressure regulators prevent the water pressure from rising above the limits allowed for the drip emitter to operate normally. They don’t increase water pressure if it is too low. Match the pressure regulator to the pressure range recommended for correct operation of the emitters. It’s more complicated with a large drip irrigation system. In cases like these, use adjustable pressure regulators.

Flushing can involve the use of valves, screw caps or be as simple as this figure 8.

            Flush caps or valves must terminate all drip irrigation lines that carry water. It is important to “flush” these lines by opening the irrigation line when the system is operating and let the water run until it comes out clean. Open each flush cap sequentially for each drip irrigation line the same time the filter is cleaned. Flush the line if repairs are done on the system that allows dirt to enter that might plug emitters. The number one reason for failure of a drip system is not flushing drip irrigation lines and cleaning the filters regularly and after repairs.

Air release valve manufactured by Jain Irrigation. It is inserted directly into polyethylene drip tubing to exhaust air in the drip lines. Water forces it shut.

            

Air release valves like this one from Netafim are also made to be screwed into PVC irrigation pipe as well.

Air release valves are an add-on to the drip system if trapped air is a problem or takes a long time for the drip emitters to start dripping water. Air release valves are inexpensive and exhaust trapped air in the system quickly before the irrigation lines become fully pressurized with water. They are usually installed at the end of a drip irrigation line or in combination with a flush cap or flush valve.

Adjustable drip emitters are convenient because you can open or close the emitter to deliver more or less water. But they are not precise and are not pressure compensated.

            Adjustable drip emitters are not “pressure compensated”. This means they deliver water at variable amounts depending on the water pressure and their elevation relative to other emitters. One reason I don’t like adjustable emitters is because of their lack of precision; when one adjustable emitter is opened to allow a greater flow of water, less water flows from the other emitters on the same line.