What happens when you replace an inground pool liner

Replacing an inground pool liner means draining the pool, removing the old vinyl, and installing a new one in its place. The job takes two to four days for most residential pools and requires basic tools—a wet vacuum, utility knife, measuring tape, and a liner installation kit. You can do this yourself if your pool is in good condition, though hiring a professional costs $1,500 to $3,000 and removes the physical labor.

The liner itself costs $800 to $2,500 depending on pool size and vinyl thickness. A 15-by-30-foot pool with 48-inch walls typically needs a liner in the $1,200 to $1,800 range. Before you start, inspect the pool walls and floor for cracks, sharp objects, or rough spots—these will tear a new liner when ready, so they must be repaired first.

Key Takeaways

  • Drain the pool completely, then inspect the walls and floor for damage, rust, or sharp edges that could puncture the new liner.
  • Remove the old liner by cutting it into strips and pulling it out, then clean the pool structure thoroughly to remove algae, dirt, and debris.
  • Measure your pool accurately (length, width, and depth) and order a custom liner that fits your specific dimensions and wall height.
  • Install a protective base layer, position the new liner, and fill the pool slowly while smoothing out wrinkles as water rises.
  • Trim excess liner at the top and reinstall the coping or deck edge, then reattach the skimmer and return fittings before running the pump.

Drain the pool and inspect the structure

Turn off the pump and filter system. Locate the main drain valve at the lowest point of the pool and open it, or use a submersible pump to drain water into a safe location away from the foundation. Draining takes 12 to 24 hours depending on pool size. Do not drain during heavy rain—standing water in the pool helps prevent the structure from shifting.

Once empty, walk the floor and walls with a flashlight. Look for cracks in concrete, rust spots on metal walls, sharp rocks, or protruding nails. Mark any damage with tape. Small cracks (under 1/8 inch) can be sealed with pool putty or concrete patching compound. Larger cracks need professional repair before the new liner goes in. Rough concrete should be smoothed with a concrete grinder or rubbed down with a stone block.

Remove any metal fittings, ladders, or light fixtures that protrude into the pool. These will be reinstalled after the liner is in place. Sweep the entire floor and walls to remove loose debris, algae, and dirt.

Remove the old liner and clean the pool

Cut the old liner into manageable strips using a utility knife. Start at the top edge and work downward in 3-foot-wide sections. Pull each strip out and dispose of it. This step is dusty and physically demanding—wear gloves and a dust mask.

Once the liner is out, scrub the pool floor and walls with a stiff brush and a mixture of water and mild detergent. Pay special attention to corners and seams where algae and mineral deposits accumulate. Rinse thoroughly with a garden hose or pressure washer set to low pressure (under 1,500 PSI) to avoid damaging the pool structure.

Inspect the pool again after cleaning. Any damage you missed will now be visible. If you find new cracks or soft spots, stop and repair them before proceeding. A new liner will not hide structural problems—it will only make them worse.

Measure the pool and order the new liner

Accurate measurements are critical. You need the length, width, and depth of the pool, plus the height of the walls above the waterline. Measure from the bottom of the pool to the top edge where the coping or deck begins. Use a measuring tape and write down all dimensions.

Most inground pools have walls that are 48, 52, or 54 inches tall. If your pool has a deep end and shallow end, measure both and note the average depth. Take photos of the pool shape and any unusual features—steps, benches, or curved sections—and bring them when you order the liner.

Contact a pool supply company with your measurements. They will calculate the exact liner size and thickness you need. Standard vinyl thickness is 20 mil (thinner, less durable) or 28 mil (thicker, longer-lasting). A 28-mil liner costs more but typically lasts 10 to 15 years instead of 8 to 10. Custom liners take one to two weeks to arrive, so order early.

Install the base layer and position the new liner

Before the new liner goes in, lay down a protective base layer. This is usually 1/2-inch foam padding or a specialized pool liner pad that costs $100 to $300. It protects the liner from punctures and extends its life. Unroll it across the entire floor and up the walls, overlapping seams by 6 inches. Tape seams with waterproof tape.

Unfold the new liner and lay it flat in the sun for 15 to 20 minutes to warm it up and make it more flexible. Carefully position it in the pool, starting at the center of the floor and working outward. Smooth out large wrinkles as you go. The liner should hang evenly over all four walls with roughly equal overhang at the top.

Place a few sandbags or weights around the top edge to hold the liner in place while you fill. Do not find it permanently yet—you need to adjust it as water rises.

Fill the pool and smooth the liner

Turn on the pump and begin filling the pool slowly. As water rises, walk around the pool and smooth out wrinkles from the center toward the walls. Use your hands or a soft brush to guide the liner into corners and against the walls. This is the most important step—wrinkles that are not smoothed out now will be permanent.

Fill to about 6 inches of depth, then stop and check for major wrinkles. Smooth them out, then continue filling. Repeat this process every 12 inches of depth. The entire filling process takes 8 to 12 hours. Do not rush it—slow filling gives you time to adjust the liner properly.

As the water level rises, the weight of the water will pull the liner down and into place. By the time the pool is full, most wrinkles should be gone. Small wrinkles (under 1/4 inch) are normal and will flatten out over a few days as the liner settles.

Trim the liner and reinstall fittings

Once the pool is full, trim the excess liner at the top. Leave 6 to 12 inches of overhang beyond the coping or deck edge. Use a utility knife and cut carefully—do not cut into the coping itself. The overhang will be tucked behind the coping or held in place with a liner lock system, depending on your pool design.

Reinstall the skimmer basket, return fittings, and any other equipment that was removed. These typically bolt or screw back into place. Make sure all connections are tight and sealed with plumber's tape to prevent leaks.

Turn on the pump and filter system. Run the filter for 24 hours continuously to clear any debris from the new liner. Check the water level daily for the first week—new liners sometimes settle and the level may drop slightly. Top off as needed.

Common mistakes to avoid

The most common error is not repairing pool damage before installing the new liner. Cracks, sharp edges, and rough spots will puncture vinyl when ready. Spend time inspecting and fixing the pool structure first.

Another mistake is rushing the filling process. Filling too fast prevents you from smoothing wrinkles properly, and you end up with a permanently wrinkled liner. Fill slowly and adjust the liner every 12 inches of depth.

Do not skip the protective base layer. It costs a few hundred dollars but adds years to the liner's life by preventing punctures from small rocks or rough concrete. Skipping it to save money usually costs more in the long run.

Finally, do not overtighten fittings or coping fasteners. This can warp the liner or damage the pool structure. Tighten firmly but stop when you feel resistance—do not force it.

Frequently Asked Questions

Can I patch a liner instead of replacing it?

Small punctures (under 1/4 inch) can be patched with a vinyl repair kit, which costs $10 to $30. Larger tears, multiple punctures, or leaks at seams usually mean the liner is failing and replacement is more cost-effective. If your liner is over 10 years old, replacement is typically the better choice.

How long does a new pool liner last?

A 20-mil vinyl liner typically lasts 8 to 10 years. A 28-mil liner lasts 10 to 15 years. Lifespan depends on sunlight exposure, chemical balance, and how well the pool is maintained. Pools in direct sun with poor water chemistry fail faster than shaded pools with balanced chemistry.

Do I need to drain the pool completely?

Yes. You cannot remove an old liner or install a new one with water in the pool. Partial draining will not work. Plan for the pool to be out of service for at least three to four days during the replacement process.

What if I find cracks during the inspection?

Small cracks (under 1/8 inch) can be sealed with pool putty or concrete patching compound. Cracks larger than 1/4 inch need professional repair—a concrete contractor can patch or seal them. Do not install a new liner over unrepaired cracks, as they will continue to grow and damage the liner.

Can I install a new liner over the old one?

No. The old liner must be completely removed. Installing a new liner over an old one traps moisture, promotes mold growth, and the old liner can shift and tear the new one. Always remove the old liner completely and inspect the pool structure before installing the new one.