How to Caulk Your Inground Swimming Pool

Written by Michael Dean
April 27, 2023

caulking a swimming pool

Whether you’re new to the world of inground pools or you’ve had your pool for decades, there is one problem that all pool owners with concrete pools or decking are bound to encounter sooner or later – cracks or holes in the caulking. If the cracks and holes grow larger, the caulking may fail and cause some major problems for you.

Luckily, the solution to removing and replacing pool caulk is relatively simple. So, let’s dive in and discuss why caulk cracks, why you should replace it ASAP, and how to do it!

Main Takeaways

  • Caulk protects the pool’s expansion joint, allowing moisture to flex the space between the pool and the deck and providing space for concrete to expand and contract.
  • Caulk also blocks the expansion joint from debris and organic matter like leaves.
  • Most pool owners will need to repair and replace caulk annually. You should fix caulk as soon as you notice damage, such as creases or cracks in the caulk.
  • To replace pool caulking, you’ll need to scrape away the old caulk, dry the area, place the foam backer joint in the joint, then fill it with caulk. When you’re done, walk around the pool to check if any area needs more caulk. Finally, use a damp towel to straighten the caulk.

The Purpose of Caulk and Why You Need Fresh Pool Caulking

Caulk serves various purposes, from earthquake protection to allowing moisture to safely flex the space between a pool and a deck to providing space for concrete slabs to expand in the warmer months. Caulk’s primary purpose is to protect the pool’s expansion joint.

Expanding forces are constantly working on your pool. Wherever your home’s climate and location are, forces strain the caulking in your pool. This is particularly true if you live in a state where winter brings a freeze. In the pool’s lining and hidden away in all the concrete slabs, water freezes and expands, causing cracks in the caulking.

This video demonstrates what can happen to a crack in a pool if it’s not taken care of early.

Likewise, in warmer climates, the concrete surrounding pools expands just like ice. Since the caulking lines the concrete pool, some tremendous forces are working to damage it.

Caulk also blocks the expansion joint from dirt, sand and stone particles, and biomass like leaves. If this excess material gets into the expansion joint, it could exert pressure that unmounts tiles or cracks the pool itself.

So, we’ve discussed what caulk does for your pool, but why do you need fresh caulking? Why so often? One reason many people apply new caulking is simple: it looks great!

But, in all seriousness, there are many reasons for regularly repairing caulk beyond improving the curb appeal of your pool.

First of all, not every pool needs caulking. However, the overwhelming majority do. If your pool fits any or all of the below criteria, fresh caulking is necessary:

  • Inground pool
  • Has concrete decks
  • Or concrete slabs
  • Has traditional coping stones installed around the perimeter

No matter which brand of caulking you use, all pool owners should look for noticeable cracks or creases in the caulk on the expansion joint. The majority of pool owners repair and replace caulk annually. If you have found the process of applying caulk difficult in the past, Home Depot has a visual aid that will make you a pro in an afternoon.

Finally, once the caulk becomes damaged, water and dirt will almost immediately fill the expansion joint. As soon as that happens, the pool’s integrity could start to diminish.

How Much Caulk Do You Need?

Measuring the amount of caulk your expansion joints require depends on your pool model and how it was installed. When you investigate the expansion joints before cutting out the old caulk, it’s a good idea to bring a small ruler that can fit in the joint. Take depth measurements from three to four locations around the pool and find an average.

Generally speaking, the complete job of replacing your caulking will take several tubes of waterproof caulking applied to a depth of at least ⅜ of an inch — depending on the joint.

Your expansion joint is typically ½ the width. That means most pool joint widths fall somewhere between ¼” to 1″. To estimate how many tubes of caulk you’ll likely need, use the following guidelines:

  • Joint Width: 0.25’’ — Tubes per 10 ft circumference: 0.1
  • Joint Width: 0.5’’ — Tubes/10’: 0.3
  • Joint Width: 0.75’’ — Tubes/10’: 0.6
  • Joint Width: 1’’ — Tubes/10’: 0.9

How To Replace Pool Caulking

Okay, you’re ready to start the DIY job of removing and replacing your inground pool caulking! Before starting, this job will likely cause some strain in the knees and back. Bring some towels to give your kneeling body some relief while you work.

Without further ado, here’s the method we’ve developed for repairing and replacing inground pool caulking, which we think is the simplest to pull off. There’s no real difficulty in the process, but it’s essential to be vigilant, keep the joint clean, and be accurate with your depth measurements.

  1. Sweep or use a leaf blower to clean the ground around the pool of all grit and dirt.
  2. Use a putty knife or blunt, thin tool to scrape away all the old caulk. Sweep off all the residual caulk from the ground again.
  3. If the tile or concrete has moisture or water on it, wait for it to dry to wipe away the water. The joint must be bone dry before applying the new caulk.
  4. Take your foam backer rod and place it in the joint firmly so that it fills every surface at the bottom of the joint.
  5. With the foam in the joint, load your caulking gun with the caulk. Remember to snip the end of the caulk canister to allow it to flow.
  6. Make your way around the pool, releasing a thick bead of caulk as you go. NOTE: It’s always preferable to overuse the caulk. Underuse can result in joint failure.
  7. After clearing the pool’s circumference, wipe away the excess caulk with a putty knife.
  8. Make several trips around the pool, checking for areas needing more caulk. Fill them immediately before they begin to dry.
  9. Use a damp towel to straighten the caulk’s contour. You’re bound to make a squiggle with your caulk gun somewhere!
  10. OPTIONAL: Some pool owners will apply colored sand to the still-tacky caulk to help make the caulk blend in with the pool’s color scheme.
  11. After 24 hours, the caulk should be dry and ready for 1-5 years of service.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

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Final Words

With a successful DIY inground pool caulking project well done, it’s time to relax and enjoy your pool the way it was meant to be enjoyed! Taking care of your expansion joints is well worth the effort every few years since it gives you the peace of mind to know your pool will not crack or lose tiles for a long time.

Repairing your pool caulking is something every responsible pool owner should take seriously. However, the repair process doesn’t have to be very serious at all. With a store of quality waterproof caulk, measurement tools, and a little patience, just about anyone can complete this project in a few hours.

Questions? Don’t hesitate to shoot me a message.

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