Something – we suspect a chipmunk – is chewing through the wires in our irrigation control valve box. We clean it out and fix the wires, only to have it happen again and again. Any suggestions? -Beth

You’re not alone – one of the toughest challenges in a home irrigation system is preventing damage from gnawing and nesting critters such as chipmunks, rats, squirrels, and gophers. Those irrigation control boxes are like a perfect piece of turnkey real estate for rodents – they can’t resist moving right in!

Here are some tips for keeping your irrigation system safe from pests.

Rodent-Proofing an Irrigation Valve Control Box

The rodent solution is deceptively simple – you have to protect the irrigation valve control box so that they can’t get in, but that’s easier said than done! To rodent-proof your irrigation valve box, you’ll need to investigate to see if you can determine if they’re getting in through:

Sharp gravel can deter rodents.

• Control Box Openings: Make sure all plumbing openings in your valve control box are screened or tightly packed with coarse steel wool or copper mesh such as Stuf-Fit. If you have to cut the box to accommodate pipes or wires, take care to cut the hole exactly the right size, with no room for a rodent to squeeze through around the pipes.
• Control Box Lid: The lid of your box must be firmly sealed to keep out both animals and debris. Weigh down the lid, or wire it shut, to keep clever rodents from lifting it and scampering through.


1/4" wire hardware cloth.

• Control Box Bottom: A lot of prefabricated plastic valve boxes don’t have bottoms, because rainwater needs to drain straight out. To keep rodents out, you’ll have to create a bottom that they won’t dig through. Try settling your valve box on a 4” thick layer of sharp gravel or PermaTill Vole Bloc, and backfilling around the box with the same material. For added protection, you can line the bottom and sides of the box with 1/4″ hardware cloth mesh, to create a permeable floor that animals can’t get through.
• Control Box Sides: Most irrigation valve boxes are made of strong but lightweight plastic that withstands the stress of underground use. However, if animals are chewing through the plastic, you may want to opt for a stronger material such as concrete or cast iron.

Unfortunately, some rodents seem to devote their lives to outsmarting even the best laid plans, and you’ll need to make sure your measures are working. Keep an eye on your valve box, remove any nesting material you see, and immediately seal off any openings or evidence of chewing.

Further Information

• Valve Filter and Regulator Detail (irrigationtutorial.com)
• How to Deal with Moles in Your Yard (article)
• How to Deal with Voles (Field Mice) in Your Yard (article)
• How to Keep Squirrels Away from Your Bird Feeder (article)

Tags: , animals, irrigation, lawn irrigation, pests