Swimming Pool Hack: No-Drain Acid Wash

Do you have a plaster pool? Are the pool stains and scales starting to look unruly or spot treatments no longer feasible? Has the local pool guy in the white van recommended to drain your pool and do an acid wash to remove all of the stain and scale build-up? Well, there’s a way around that with today’s swimming pool hack, the no-drain acid wash!

What is an Acid Wash?

First off, before we go ahead and explain what a no-drain acid wash is, let’s first go over what pool acid washing is. Basically, to acid wash a pool, the pool is drained and then hosed down with a water-acid solution to strip a thin layer of your pool surface to get rid of all of the stain and scale build-up. This isn’t “stain removal” per se, this is actually peeling off a layer of your pool (like an onion) and taking along all of the stains and scale with it.

This is probably the most effective way to bring your pool surface back to its brand new condition. But this comes at a cost. Draining the pool, re-balancing it, and you’ll need to get a professional to do it. This will cost quite a bit, about $400-$500 for the acid wash for a standard sized pool plus whatever it will cost to refill the pool water and the chemicals needed to rebalance the pool.

Note: Always be aware of the Australian Water Restrictions if you plan to acid wash your pool, you don’t want to get in trouble for draining your pool in the middle of a drought!

What is a no-drain acid wash?

In a nutshell, a no-drain acid wash is lowering the pH level of your pool so that your pool water becomes acidic and alkalinity close to zero. When this level is hit, some vigorous scrubbing will be required to peel off a bit of the pool surface, essentially giving you an acid wash without draining the pool.

What do you need for a no-drain acid wash?

It only takes a couple of pool chemicals to do a no-drain acid wash on your pool and a couple of chemicals to bring it out of the acid wash condition. Of course, we’ll be needing some tools as well but these are pretty basic.

Since we’re going to be lowering the pH of your pool to acidic levels, it goes without saying that we’ll need some pH down tablets to drop our pH. We’ll also need a testing kit to ensure that our levels are where we need to them to be. Note: Use a reagent test kit like the Water TechniX 5 in 1 Pool test kit to test your pH and Alkalinity levels, a test strip won't be of much use to you when dropping your pH levels drastically.

SEE ALSO: How To Treat Pool Water For The First Time

To clean the pool, you’ll just need a steel algae brush, yes, steel because we’re going to be scrubbing the pool multiple times over a 3-day period to give it a good exfoliating effect.

After the no-drain acid wash, you’ll need to raise the pH levels so you’re going to need a good supply of alkalinity up as well!  

Note: You’ll need to get some metal sequestrant from your local or online hardware supply store if you’re in an area that has heavy metals in water and basically just a precaution to prevent excess clouding up of your water.

SEE ALSO: Our Top Tips For Cleaning A Pool Without Using Chemicals

No-drain acid wash preparation

Here are some things to keep in mind to prepare your pool for a no-drain acid wash. Remember, once you start the no-drain acid wash process, you must commit to seeing it through all the way because you’re going to be dramatically changing the chemistry of your pool water.

  • Clear weather and no rain - Check with your local weather forecasts and look for a 3-day window with no rain, thunderstorms, or high wind warnings because we want our pool to remain as clean as possible for the entire no-drain acid wash treatment period.
  • Make sure the pool is super clean - Up to a week before no-drain acid washing your pool, make sure that your pool is super clean. This means that you should shock your pool to kill off any organic material in the pool, over-filter it by running your pump for a few days before starting the no-drain acid wash.
  • Pre-scrub your pool - scrub your pool surfaces, remove all debris, again, make sure that your pool is super clean before starting the no-drain acid wash process.
  • Remove all metal from your pool - Remove your ladders, rails, pool lights, and anything metal because the water will be very acidic and you don’t want them to get corroded with the treatment.
  • Remove other pool accessories - If you’re the type that leaves pool cleaners and robotic pool cleaners in the pool, it goes without saying that you should take them out so that they don’t get eaten by the acidic water.
  • Overfill Pool and turn off pump (and valves!) - Once you’re ready to start the process, overfill the pool to the top level to make sure every pool surface is underwater and shut off the power to your pool pump to make sure that it doesn’t turn on accidentally in the middle of the process as the acidic water can damage the internals of your pump.

The no-drain acid wash process

Once your pool is all locked up, overfilled and ready to go:

  • Now apply your pH down or Sodium Bisulphate to your pool. If your sodium bisulphate comes in tablets, you can crush them up to allow for easier dissolving. As a rule of thumb, we’ll need to use around 4kg of sodium bisulphate for every 20,000L of pool capacity to drop the pH down to 1 and to get the alkalinity level to 0.
  • After broadcasting the sodium bisulphate around the pool, scrub the pool immediately! This will help dissolve the powder and lower your pH down faster. After scrubbing test your water to see if you’ve reached pH 1 and alkalinity zero. If not, add more sodium bisulphate.
  • For the next 3 days, scrub your pool surfaces every few hours and keep testing your pool water to ensure that your pH levels are still low.

  • After 3 days, your pool surfaces should be fairly clean so it’s now time to add the pH increaser/alkalinity up.
  • Now, raising the pH isn’t the same as lowering the pH. When increasing the pH and alkalinity ppm of your pool you should divide it into three equal doses of 6-12 hours in order to prevent the water from clouding up.

By adding it in spaced doses, there will be minimal clouding up but it should clear up by the time you add the next dose. After you add the final doses, check your pH levels, it should be at the normal levels (7.2-7.6) and Total Alkalinity should be around 80-120 ppm, and once you’ve reached those levels, you can open up the pipes/valves and turn on your pumps. (Don’t forget to put back the stairs, lights, and everything that you removed from the pool before starting)

Note: Don't forget to drain your pool water back to its normal levels!

Post No-Drain Acid Wash Notes

Here are some notes to keep in mind after doing a no-drain acid wash.

  • There will be some times where the raising of alkalinity and the scrubbing of the pool will cause particles to stay in the pool. To deal with this, some clarifiers will be in order.
  • For the next week or so, keep monitoring the pH levels and Alkalinity levels to see if they have already stabilised.
  • Depending on how much scale you've removed, your pool's calcium levels may have fluctuated during the treatment, so test your calcium levels and ensure that they're below the 180ppm levels to prevent further scaling.
  • If your alkalinity levels are still fluctuating, add a good dose of algaecide to prevent algae growth. Only add chlorine or shock your pool once the alkalinity levels have stabilised.


While it’s a lot of work, the no-drain acid wash is an economical way of clearing your pool of any staining and scaling. Again, this is a very manual and labor intensive process. Do not use any automatic pool cleaner or robotic pool cleaners during the process as these will be damaged by the acidic water.


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Happy swimming :)

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