How To Repair Pool Plaster Underwater

Written by Michael Dean
July 5, 2023

repairing pool plaster underwater

If you have noticed unsightly cracks, holes, and stains on your pool plaster, it is time to have that plaster repaired before it gets any worse. You should avoid draining your pool water as it can further damage your plaster and can be costly to replace. So, you may wonder if there’s a way to repair pool plaster underwater.

In this article, I will provide you with everything you need to know on how to repair pool plaster underwater, why you need to repair it in the first place, and go over common issues you may encounter with pool plaster.

Main Takeaways

  • The most common issues with pool plaster are staining, streaking, cracking, erosion, etching, and delamination.
  • Pools need not be drained if only a small amount of plaster needs to be fixed.
  • Underwater epoxy putty and underwater pool plaster can be used to repair cracks and holes while the pool is still full.
  • Pool plaster repairs done underwater will cost you a maximum of $75, whereas replastering the entire pool will cost you a minimum of $7,000 per 1,000 square feet.

Common Issues With Pool Plaster (When The Pool Is Full)

No matter how well the plaster is installed in your pool, over time, pool plaster can develop numerous problems that every pool owner should know how to identify. 


Staining is one of the most common problems that pool plaster develops underwater, and this is because of organic matter that falls into the pool. Things like leaves, grass, flowers, and even berries that fall in the pool can stain the pool plaster in a matter of hours.


Etching is a common problem most pool plaster owners encounter. Etching is when the pool plaster becomes exceptionally rough, with bumps and dents forming on the surface of the pool plaster. The number one cause for this is unbalanced water chemistry.


Cracks in the plaster are another problem that often plagues pools. While it may seem harmless at first, even the smallest cracks can become a bigger problem later on as algae and harmful bacteria can begin to grow in the plaster.


The final problem, delamination, is quite a serious problem. This happens when the pool plaster separates from the concrete underneath. You have a delamination problem if you see white blisters or bubbles forming in the plaster.

Issues Caused By Unbalanced Chemicals

The debris and other outside elements can also cause the water balance to become unbalanced, another cause of many pool plaster problems. The changes in the pool water chemistry can affect the pool plaster causing staining, erosion, and scaling, which is a build of minerals like calcium.

Should You Empty Your Pool Before Fixing Plaster? 

Many people automatically assume that you need to drain your pool when repairing pool plaster, but this isn’t always the case. You do not need to empty your pool before fixing plaster if the damage is not that bad or if it is just a small area.

On the other hand, if the damage is extensive and requires the entire pool to be repaired, you must drain the pool first. Otherwise, there are plenty of pool plaster repair products that work underwater.

Step-By-Step Guide: How To Repair Pool Plaster Underwater

Here’s my handy step-by-step guide on how to repair pool plaster underwater.

Tools Needed

  • Paint scraper
  • Wire brush
  • Underwater epoxy putty or underwater pool plaster
  • Trowel or putty knife
  • Goggles (optional)

Step One: Scrape Away The Problem

Before you begin, you may want to put on a pair of goggles if the area you’re repairing is at the bottom of the pool.

This may seem counterintuitive, but to fix a part of the plaster, you will need to scrape away the plaster surrounding the issue, whether it be a crack, hole, or something else. Use a paint scraper and run it along the edges of the problem area. You want to open and expose as much of the problem area as possible.

Step Two: Clean The Area

Once you have completely exposed the problem area, use a wire-bristled brush to gently wipe away any excess debris and dirt. If it’s a crack you’re fixing, ensure you’ve brushed away any algae that may have been growing in the crack.

Step Four: Replaster The Area

You can use underwater epoxy putty or underwater pool plaster for this step.

Epoxy Putty

  1. Cut equal amounts of part A and part B of the putty.
  2. Combine parts A and B together to form the mold, and make sure it is well combined.
  3. If you are repairing a hole, it should be the shape of a ball. If you are repairing a crack, it should be in the form of a rope.
  4. Push the combined putty into the hole or crack of the pool wall.
  5. Using your fingers, smooth the putty and edges down.

Underwater Pool Plaster

  1. Mix the plaster in a container outside before entering the pool, following the manufacturer’s instructions.
  2. Once mixed, roll the plaster into a ball.
  3. Press the plaster ball into the hole or crack in the pool.
  4. Use a trowel or putty knife to ensure the plaster is pushed in properly and smoothed out.

The epoxy and plaster will cure underwater. 

Underwater Pool Plaster Repair Cost

Repairing pool plaster while it is still underwater is much cheaper than draining and refilling the entire pool. The cost of repairing pool plaster will vary depending on how much product is needed and what product you choose. For example, a tub of underwater pool plaster repair can range from $30-$90, and underwater epoxy putty is around $10-$60.

On the other hand, replastering an entire pool can set you back around $7,000 per 1,000 square feet. Not to mention the cost of draining and refilling the pool, which is also costly; using a professional will cost you between $70 and $150. And that doesn’t include the water cost.

Repairing pool plaster underwater is overall a much cheaper option.

Why Do You Need To Repair Pool Plaster?

Pool plaster issues need to be repaired as soon as possible because problems with plaster that are left to grow can lead to severe structural damage and can eventually lead to replastering.

If you are hesitating about repairing the plaster, remember that it is much more costly to replaster the whole pool than to fix a small section.

For example, cracks and holes that are not repaired can lead to algae growth. The algae will then spread and grow inside the pool structure, compromising the integrity of the pool walls.

When To Call A Pool Professional To Help With Underwater Repairs

While you can certainly repair those tiny holes and cracks in your pool plaster by yourself fairly easily, there may come a time when you will have to call a professional to help with underwater repairs to ensure that it gets done correctly.

If you have already repaired the same crack or hole multiple times and the putty or plaster keeps popping off, then it may be time to call a professional to do the repairs. Sometimes, you may need a professional to tackle more stubborn stains without damaging the pool plaster or messing with the pool water’s chemistry.

Finally, you should call a professional to help with underwater repairs if you are unsure how to fix it. The last thing you want to do is to make an even more costly mistake. Only repair your pool plaster yourself if you are confident that you can do it.

Do you have more questions about pool plaster? Let me know!

Scroll to Top