Well Cap: What It Does and When to Replace It

A well cap is the lid on top of your well casing. It keeps bugs, rain, mice and yard runoff out of the water you drink. A good one seals tight but still lets the well breathe through a screened vent. If yours is cracked, loose, missing or sitting crooked, get it replaced and test your water.

What does a well cap actually do?

Your casing is a straight pipe down to your drinking water. The cap is the only thing on top of it. When it fails, whatever lands on the wellhead can fall straight in.

South Carolina law takes the well cap seriously. The state's well standards, Regulation 61-71, require a sanitary seal on top of every well casing. That seal can't have any opening that lets contaminants or foreign matter inside. The same rule says new casing has to stick up at least one foot above the ground. That keeps rainwater from pooling over the top.

What are the different types of water well caps?

Most caps fall into three groups. Boshart, a well parts maker, sorts them this way.

A plain cap has no wires running through it. You'll usually see one on a jet pump well, where the pump sits in a pump house. A conduit cap lets the wiring for a submersible pump come out the top and run to a conduit. A watertight, or sanitary, well cap seals all the way around the casing and the wiring. It uses a screened vent so air moves and pests stay out.

The right cap depends on your pump and your casing size. That's why we look before we order anything. Not sure which one you have? Send us a photo when you call.

Does my well cap need a vent?

Yes, almost every well needs a vent. A well breathes as the water level rises and falls. Without air moving in and out, the system can pull a vacuum.

The vent is also a weak spot. SC's rule says any vent has to keep out contaminants, insects and rainwater. A torn or missing screen is an open door for spiders, wasps and small critters. We've pulled all of those out of wells over the years.

What are the signs your well cap needs replacing?

When did you last look at yours? Walk out to the wellhead today. Cracks, rust holes or a split plastic cap are easy to spot. So is a cap a mower knocked loose or crooked. Missing bolts and a torn vent screen count too.

Your water can tell you first. A bad taste after heavy rain is one clue. So is cloudy water or a failed bacteria test. A dead bug in a faucet screen is another. Any of those can mean the cap or seal is letting surface water in. Our article on coliform bacteria in well water covers how that happens.

What happens after a well cap replacement?

At Austin Drilling, every well cap replacement starts with the whole wellhead, not just the lid. A loose cap sometimes hides a cracked or crooked casing underneath. If we find that, well casing repair comes first.

Once the new cap is on, test the water. If anything got in while the cap was bad, a shock chlorination usually clears it. Then a follow-up test confirms it worked. The cap check also belongs on your regular well water maintenance list.

FAQ

How do you cap an old well?

South Carolina says any well taken out of service has to be sealed with a watertight cap or seal. That covers the old well on a property that now runs on city water. It also covers a well whose pump was pulled or stolen. Tell us if you might use it again. If not, it should be properly abandoned and sealed.

Can I replace a well cap myself?

We don't recommend doing that one yourself. On most submersible wells, the pump wiring runs right through the cap. The cap also has to match your casing exactly. Austin Drilling will fit the right one and check the wiring and seal.

How often should I check my well cap?

Look at it every season and after every big storm. Check again after yard work near the wellhead. The whole check takes about two minutes.

Is a missing well cap an emergency?

Treat it like one for drinking water. Switch to bottled water until the cap is back on and a test comes back clean. Call Austin Drilling at (803) 926-5402 in West Columbia or (803) 926-7080 in Newberry. We're open Monday through Friday, 7am to 6pm, and Saturday by appointment.