Most Frequently Asked Questions about Irrigation Valve Boxes

If you are installing a sprinkler system, then you will need to install valve boxes to hold the shut off sprinkler valve and other pipes and connections. Irrigation valve boxes are important parts of the sprinkler system, and if you have a faulty or defective valve box it can be monstrous hard to get your water shut off in the winter before the snow sets in. If you’re comparing various valve boxes or need advice, look here for answers to homeowner’s frequently asked questions about irrigation valve boxes.

Question: The sprinkler valve box for my front yard will be located next to my driveway (about 6 inches from the concrete), and the sprinkler installing contractor I’ve hired insists that I get a higher quality valve box because of this. Why would this be necessary?

Answer: If you ever anticipate teenage drivers pulling into your driveway (or a bunch of crazy friends), you will certainly benefit from a higher quality valve box. There is a chance that acarwill roll over the valve box lid at some point. If it isn’t strong enough, it will crack. Cracked lids can smash into the valve box and even damage the pipes and valves inside them. If driven over, a broken valve box lid can also get stuck inside your valve box and make it hard for you to open the lid again. Your contractor isn’t just trying to make extra money off your parts here. Most experts recommend higher quality boxes and fittings if the valve box will be located near the driveway. Remember that bikes, motorcycles, snow blowers, and even lawn mowers can potentially damage a valve box lid that’s flimsy and not made to stand up to some abuse. You may not need a commercial grade lid or box in this situation, but definitely go with a high quality residential valve box.

Question: I live in the Phoenix, Arizona metro area. High temperatures here melt some types of plastics, and I’m wondering how this will affect what type of valve box I should install for the small sprinkler system I’m putting in for a patch of grass in the back yard. The PVC molded plastic valve boxes I’ve been looking at have a melt index of 10. What does that mean, in terms of how hot it will take before the plastic melts?

Answer: A melt index of 10 means that at about 154 degrees Celsius (or 309 degrees Fahrenheit), the plastic would begin to melt. Even considering Phoenix’s 120 degree high temperatures, and the fact that a plastic lid on the ground gets 25 to 35 degrees hotter than the air, you should be fine. You won’t notice any softening of the plastic or melting if you get a valve box that has this high a rating. Cheaper valve boxes often melt or soften at temperatures above 110 degrees, but this one you’re looking at with a melt index of 10 would be a good one to pick since you’re in such a hot climate.

Question: What does it mean if a valve box states that it meets the specifications of ASTM A48? Does this mean it is environmentally friendly?

Answer: No, ASTM A48 requirements are not about recycling, green building, or being made of environmentally friendly materials. If valve box components meet ASTM A48 specifications, that means it has passed certain international strength tests. Commercial cast iron valve boxes or valve box lids are often subjected to ASTM A48 tests since they must stand up to heavy wear and tear.

Question: How deep should I install the irrigation system valve box underneath the earth? I am worried about hitting corners of it with the lawn mower, so I want to make sure it’s deep enough that even if the ground shifts my lawn mower won’t clip the corners or scar the lid.

Answer: You want your lid to be flush with the ground level. If the lid sits higher than the ground, you do risk not only hitting it with the lawn mower but also tripping people. You don’t want the valve box sunk too deep though, because if it’s too deep and a bike riding across the lawn crashes down a few inches to the lid it could cause the lid to crack. You are also more likely to get water pooling inside your valve box if it’s set too deep in the earth, and it is often harder to remove the lid if the box is set too deep.

Question: How do I know if the valve box I am getting along with my sprinkler system is eco-friendly? I am interested in green building and in LEED credits. All these boxes look alike and none of them seem to list anything about LEED credits.

Answer: Look for valve boxes that are made from recycled materials, and that have a recycling symbol stamped on them. There are many PVC or molded plastic valve boxes that meet requirements for LEED credits (the internationally-recognized green building verification system of giving credits for eco-friendly building materials and methods). You won’t find concrete or cast iron valve boxes that are going to earn you any LEED credits, since these are not recyclable.

Question: What are the advantages of a molded plastic valve box with corrugated sides, as opposed to one without corrugated sides?

Answer: The plastic corrugated sides give a high level of tensile strength to a valve box. This means that it is less likely to crack if you drop a shovel on it, or if a motorcycle or bike runs over the lawn. Cracked valve boxes can be a bother to replace, so it is usually worth it to get a sturdy design that will last and stand up to some amount of abuse, as well as climactic changes like freezing temperatures in winter or soaring high temperatures in summer. There are valve boxes that are as durable as those made with corrugated sides, but they are generally much heavier and harder to install. Plastic corrugated valve boxes are lighter weight than concrete valve boxes.

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