Catch the crap

Features - Irrigation

Knowing what filter to use is key in making sure your irrigation system runs smoothly.

April 8, 2013
Jason Stahl

There once was a landscape contractor turned comedian. At a conference of his peers, he picked out one unfortunate soul in the audience and asked, “What do you know about irrigation filters? No pressure!”

Ba-dum ching.

But seriously, it isn’t rocket science. There are some basics you need to know when you’re buying filters.

The number one concern, according to Perry Continente, product manager with Jain Irrigation, is pressure rating – particularly that it’s reasonable for the pressure of the system.

“Also, the filter shouldn’t be under pressure all the time, so basically it should be downstream of the on/off valve,” Continente says. “Other than that, it’s not very complicated other than making sure you have the proper mesh for the emission devices you’re going to be protecting.”

In general, manufacturers have minimum filtration requirements, Continente says, so he advises that you meet or exceed those requirements.

“Typically, you don’t want to have additional filtration that you don’t need,” he says. “For instance, if you have a 150-mesh minimum requirement, it’s more desirable to have 150 mesh than 200 mesh because then, all of a sudden, you’re catching stuff that you don’t need to catch.”

Graywater. Although Continente says he has not had many inquiries regarding the filtering of graywater, he knows from personal experience that it’s very difficult to filter – particularly due to the lint from washing machines.

His solution? A woman’s stocking, which he says does a great job of catching lint. Just make sure to change it out once in a while. The other trick to graywater is to not store it but use it almost immediately.

Irrigation consultant Brian Vinchesi says that those who use graywater need to be familiar with local regulations and whether or not it has to be disinfected before use.

4 Questions to Ask Your Filter Salesperson

  1. Do I need a screen filter or media filter?
  2. What size does the filter need to be (flow rate on filters is important)
  3. If it’s automatic, does it backflush at a set time or when there is pressure loss (due to the filter being dirty)?
  4. If I backflush, when I go to automatically clean the filter, how much water does my backflush use? (Because if it backflushes halfway through your irrigation cycle, you want to have some idea what’s going to happen).

“If you’re spraying it, it will most likely have to be disinfected,” Vinchesi says. “If you’re subsurface dripping it, which is what most regulations require, you will not have to disinfect it. But the problem with disinfection is that the disinfection equipment is going to require a certain level of filtration, which is going to be pretty small and depend on the UV manufacturer. If disinfection is required, you will have to find out what the manufacturer requires for filtration.”

In landscape irrigation, you’re mostly going to be filtering because you have drip, Vinchesi says. Therefore, the mesh should be in the 150 to 200 range, and you’ll be filtering at the valve because odds are your whole system isn’t drip.

“If you have a lot of drip and you’re on a non-potable water source and you don’t want to be cleaning your filters all the time, you’re probably better off putting the filter at the point of connection also, or at the water supply,” Vinchesi says.

In that scenario, you don’t want the filter to catch everything but just bigger things, so the mesh recommendation would be 80 or 100.

Rainwater. If you’re dealing with rainwater, Vinchesi says, coarse filtering is fine because you’re just trying to make sure you don’t get a leaf or stick stuck in the system. But there are more particular requirements for stormwater because it could contain sand or silt.

“The best way to handle that is to let it settle out,” Vinchesi says. “But if you’re getting it direct, you’ll need some sort of screen filtering.”

Vinchesi says that there are two types of filters, one for organics and one for inorganics. Inorganics can usually be handled with screen filtering. A caution with filters that handle organics is that it’s hard to get the organics out of the filter. Plus, they might have a tendency to grow on the filter if you’re not careful.

Water Quality.
In certain parts of the country, zebra mussels have become a major concern with filtering alternative sources of water because they require small mesh, 80 or 100. That’s why you need a water test, Vinchesi says.

Depending on the test results, you may want to automate filtration. If your water is really bad, you will most likely want to automate because your filters will need to be cleaned on a twice-a-week, daily or even more than daily basis. If your water isn’t too bad and you only have to clean your filters once a week or once a month, then a manual-type filter is in order.

If you’re using non-drip irrigation with alternative sources of water, your choice of filtration will depend on your water source.

“If your water comes from a pond or stream, you probably don’t want something too fine if you’re just doing sprinklers. You don’t want to be clogging up the little filter in the bottom of the sprinkler,” Vinchesi says. “You want to make sure you’re not getting leaves, fish or twigs in there, so you’ll probably put something in there with 1/8-inch hole size to suck up anything big so it doesn’t get out in your irrigation system or damage or clog anything, especially valves since they’re very sensitive.”

The author is a freelancer based in Cleveland.