Shop Well Caps
For wells where the water line exits through the side of the casing below ground.
Shop Well CapsWhat Well Cap or Well Seal Do I Need?
Most private wells use a well cap or well seal to protect the top of the casing. Both help keep debris out, but each is designed for a different well setup.
Step 1
Cap or Seal?
Well cap vs. well seal: both protect the top of your well, but they fit different setups.
Choose a Well Cap If:
- The water line exits through the side of the casing
- Your system uses a pitless adapter
Cap = side exit
Choose a Well Seal If:
- The pipe passes through the top of the casing
- Your system does not use a pitless adapter
Seal = top exit
Good to know: Protection depends on the specific product. Always confirm the size, venting, and whether it is watertight.
Step 2
Measure Your Well Casing
The measurement you need depends on whether you are buying a well cap or well seal. A tape measure is all it takes.
For a Well Cap: Measure the Outside Diameter
Measure straight across the center of the casing from outside edge to outside edge.
For a Well Seal: Measure the Inside Diameter
Measure straight across the center of the casing from inside wall to inside wall.
Measure the casing—not the old cap or seal. The existing part may overlap the casing and give you the wrong size.
Common sizes
These are common casing sizes. Match your actual OD for a cap or ID for a seal to the fit range listed on the product page before ordering.
Step 3
Choose the Right Well Cap or Well Seal Protection
Not every well cap or well seal offers the same protection. Compare standard, vermin-resistant, and watertight options for your private well.
Standard Well Cap or Well Seal
Everyday wellhead protection
Provides basic protection for the top of your well casing. Check the product page for fit, venting, and watertight ratings.
Vermin-Resistant Well Cap
Screened vents & tighter openings
A vermin-resistant well cap helps keep insects, debris, and small animals from entering your well.
Watertight or Sanitary Well Cap or Well Seal
Strongest wellhead protection
A gasketed, watertight design provides added protection against surface water, debris, and contaminants.
Good to know: Watertight protection is available for both well caps and well seals. Always confirm the size, fit, venting, and protection rating before ordering.
Step 4
Check the Configuration
Before ordering, match these details to your well and the product specifications.
Casing Size & Material
Confirm the actual casing ID or OD and whether the product fits steel, PVC, or both.
Vent Size
Match the required vent size so the well can equalize pressure.
Conduit or Wire Opening
Confirm the opening fits your electrical conduit or wiring.
Pipe Configuration
For well seals, check the drop-pipe size and whether you need a single- or double-drop design.
Protection Type
Confirm whether the product is standard, vermin resistant, sanitary, or watertight.
Step 5
Replace or Upgrade
Take a close look at your well cap or well seal. These are signs it may be time for a replacement:
- Cracked or damaged body
- Rusted bolts or hardware
- Missing, worn, or crumbling gasket
- Loose fit or movement
- Gaps around pipes, wires, or conduit
- Bugs, debris, or surface water getting in
Already Replacing It? Consider an Upgrade.
Replacing an older standard cap or seal is a good time to consider a vermin-resistant, sanitary, or watertight option for added wellhead protection.
See recommended picksStep 6
Shop Well Caps & Well Seals
You've identified your setup and measured your casing. Choose the product category that fits your well.
Before You Order
Can I replace a well cap or well seal myself?+
Many well caps can be replaced with basic tools. Call a well professional if wiring, the pump, drop pipe, or damaged casing must be moved.
What if my measurement falls between sizes?+
Do not round up or guess. Match your actual casing measurement to the fit range listed on the Merrill product page.
What if I still cannot identify my setup?+
Take clear photos and measurements of the casing, water-line location, wiring, and existing cap or seal before contacting Merrill or a well professional.
Ready to Protect Your Well?
Choose the product category that matches your well setup.
Still unsure? Review Cap vs. Seal