Irrigation 101

Don’t let greywater give you the blues

Greywater can present challenges to irrigation systems since this type of water is generated from activities such as laundry, dishwashing and bathing, and typically contains phosphates. If those phosphates are filtered out properly, then there are no issues with backflow preventers and pressure reducing valves. Reclaimed water or former wastewater (sewage) that’s treated to remove solids and certain impurities can also cause headaches. But surface water can present some challenges, too, says Paul Wait, national irrigation sales manager for Zurn Engineered Water Solutions. Inlets for pipes and pumps generally reside in areas where minerals are easily sucked into the irrigation system. When that happens, you introduce higher calcification and very fine sediment. “That’s just like sandpaper going through the valves, and it wears components down,” says Wait. There are specialty components, however, that are specifically designed for use in secondary water sources such as treated, reclaimed water. For example, Hunter Industries has a special valve called the ICV with Filter Sentry. The ICV has a special diaphragm made of EPDM (ethylene propylene diene monomer) rubber in the diaphragm and diaphragm seat.

This material is designed to handle chemicals such as chlorine that are prevalent in this type of water. The Filter Sentry device scrubs the diaphragm filter screen twice during each valve cycle to keep the valve operating in water with debris. And the Filter Sentry system is part of the diaphragm so it can be integrated into non-filter sentry ICV valves should the water supply change. Craig Borland, product manager for Toro, also says that it’s all about the rubber when it comes to valves. “Some of the chemicals (in greywater/reclaimed water) are harsh and you have to be careful with standard valves, asking yourself, ‘What rubber is in it?’” Borland says. “Some valves are better suited to greywater than others.” Borland says you also need to be aware of particulates. “Are you pulling from city water? Or a lake, river or well? With lakes, rivers and wells, you have to be careful of particle size in valves.” When it comes to general specifications for valves, Craig Borland, product manager for Toro Irrigation, said it varies from valve type to brand to company.

“You used to be able to easily say that a 1-inch valve was capable of 10-50 gallons per minute (GPM), but manufacturers have changed valve designs and gotten fancy,” Borland says. According to Borland, valves need to have a minimum of 10 PSI coming in or they won’t function. Some drip valves will go as low as .2 GPM. A standard one-inch residential valve needs to have a minimum of 5 GPM. Toro has a three-inch valve that can handle up to 300 GPM safely. Other 3-inch valves can only handle 250 GPM. Hunter Industries’ commercial valves can handle flow ranging from .1-300 GPM at 220 PSI, and their residential/light commercial valves have flow capabilities as low as .2 GPM up to 200 GPM at 150 PSI.

“Size the valve properly to the range the valve is designed for and for what the demand is on that zone,” Borland says. Performance specifications for backflow preventers vary from region to region, Wait says. Some are dictated by state code, while others are specified at the county level. The specs are given for the three types of backflow preventers: pressure vacuum breaker (PVB), reduced pressure principle (RP or RPZ) and the double-check. But all follow the specs for compliance offered by groups such as the American Water Works Association and the American Society of Sanitary Engineers.