An acid wash is a method to aggressively clean and remove surface stains and algae from pools using muriatic acid. The cost of an acid wash for a pool varies. Depending on the size of your pool, you can expect an estimate to be anywhere between $600 - $3000. However, you’ll also want to add on to that the cost of refilling your pool water and replacing all the pool chemicals in it. There are cases where an acid wash is the best method, such as in the case of persistent and heavy algae or metal stains, but as we mentioned, it’s the most aggressive method out there–and it’s not without risk. Before you decide to go forward, it’s worth evaluating all the other alternative options. 

The Risks of Acid Washing a Pool

Muriatic acid is highly corrosive and can be dangerous to handle. It’s also more than a surface stain remover: it’s a surface remover. The acid etches and dissolves the smooth outer layer of your pool surface. Because of that, it can cause permanent changes to your pool surface. 

• Following an acid wash, you may find the pool surface feels rough
• It may also still appear blotchy or streaky
• Acid washing can sometimes cause surface cracking
• If you have a tile or pebble surface, it can also dissolve the cement that bonds the tiles or pebbles together

Most pools should only be acid-washed 1-2 times in their lifetime. You should also only work with a licensed and experienced contractor that has liability insurance. 

Stain and algae Removal Alternatives to Pool Acid Washing

1. Diamond polishing: For concrete pools, diamond polishing is a highly effective stain removal process that can be done without draining pool water. This method can not only remove stains, but will also polish and smooth out any rough areas. While it’s typically the same cost or more expensive than an acid wash (estimates can also run $600-$3000 approximately) it also doesn’t carry the same risks of damage to your pool surface. However, it should only be done by an experienced professional.
   
   
2. Pressure washing: If your surface stains are mild, pressure washing is another great alternative that can effectively remove stains and algae from concrete, aggregate, and pebble pool surfaces. You will still need to drain pool water and replace it, along with the necessary chemicals, as well as take care not to damage the pool surface but as a general rule, this is a far gentler method than acid washing.
    
3. No drain acid washing: A no drain acid wash involves making your pool water more acidic, letting the acidic water work on removing stains without draining the pool. While it doesn’t work for all pool types, and does require closing down the pool for several days, it costs far less than a full acid wash: approximately $200-$400 for a professional wash. It can also be far gentler on the pool surface.
   
   With a no drain acid wash, first a metal sequestrant is added to prep the pool ahead of time, then you will double the amount of sanitizer you add, filter and vacuum twice as much, and then turn off the pump and pool filter. Next, add a pH decreaser, whether that’s muriatic acid or an alternative. Add pH decreaser until the Total Alkalinity (TA) is zero. For the next 72 hours, maintain this TA and brush the pool walls each day with a steel brush, to assist the acid in stain removal. After 72 hours, your surfaces should be clean and you can begin the process of re-adjusting the alkalinity and pH: the pH should be between 7.2 and 7.6 and TA should be between 80 and 120 ppm. 

The Best Alternative to Pool Acid Washing

The absolute best alternative to an acid wash is consistent, preventative maintenance for a clean pool that includes careful water balancing and weekly brushing. Make sure you use the right brush for your pool surface: use a nylon brush for painted concrete, vinyl liners, and fiberglass, and use a steel brush for gunite and unpainted concrete. Use wide brushes for main open pool areas, and smaller corner brushes for tight spaces, such as around ladders. 

Particularly if you’re dealing with or trying to prevent algae, brushing is a simple and highly effective method for loosening the algae biofilm that loves to attach itself to the rough nooks and crannies on your pool surface. Once loosened, that allows the chlorine in the water to take care of it. In fact, you can even try a good brushing, followed by a chlorine shock, to remove existing stains. But a weekly brushing all over–not just where you see algae–will help it from building up and becoming an unsightly issue. 

Other common reasons for pool stains include calcium build-up, accumulated metals and minerals, debris, and unbalanced water. So keeping your water consistently balanced and healthy is not only better, safer, and more enjoyable for your guests, but it will also go a long way towards preventing stains. Take care to remove debris as soon as you see it, and to prevent metal and mineral build-up, you can use a sequestering agent once or twice a year to bind them together and prevent them from attaching to the pool surface. Maintaining a proper pH is another crucial step. 

Whether you’re using one of these methods to remove stains, and need to refill and rebalance your pool water, or are working on maintaining safe, clean, and balanced pool water consistently, to prevent stains, we built the PoolSharkH20 app to help. Our simple-to-use and mobile app makes testing pool water and calculating chemical adjustments easy by doing the complex math equations for you, ensuring you or your staff use the exact, correct amount of chemicals you need. Test and adjustment records are locked automatically and saved digitally, so you can always go back to reference and are always Health Department compliant. When paired with digital LaMotte WaterLink SpinTouch, pool water tests can be performed by staff in 60 seconds and are certified to NSF Level 1 accuracy–saving you time, money, and even pool chemicals.