Why We Avoid Acid Washing in Extreme Heat

Why We Press Pause on Acid Washing in Extreme Heat

We recently got a call from a customer — let’s call him Jim — who was ready to schedule an acid wash for his pool. He’d already been thinking about it for a while and finally said, “Okay, I’m ready, let’s do this.”

When we told him we could put him on our list, but wouldn’t actually drain and acid wash his pool until the weather cooled off, he was surprised: “You’re not doing acid washes right now?”

From our side, it was a simple answer: with our Arizona-style summer heat, draining a pool and exposing that plaster or pebble surface can do more harm than good. For us, it’s not worth the risk to your pool — or to your wallet.

What Really Happens to Pool Surfaces in Extreme Heat

When the temperature is consistently high, especially when it’s over about 85°F, your pool’s plaster or pebble finish is under a lot of stress. Now imagine draining all the water out and leaving that surface bare under full sun.

Here’s what can happen if you acid wash in extreme heat:

• Cracking – The surface heats up, dries out, and expands, which can lead to hairline or even visible cracks.
• Delamination and flaking – The plaster or pebble can separate from the shell in spots, causing hollow areas or chunks flaking off.
• Discoloration and streaking – Acid works faster in high heat, so an already aggressive process becomes much harder to control.
• Shortened surface life – Even if you don’t see immediate damage, repeated hot-weather draining and acid washing can shave years off your pool’s finish.

That’s why, as we explained to Jim, we wait until daytime highs are at or below about 85°F before we’ll schedule an acid wash. Until then, we’ll happily put you on a waiting list so you’re near the front of the line once it’s safe.

When It Is Safe to Acid Wash a Pool

Acid washing is a great tool in the right conditions. We usually recommend it when there are severe stains, heavy calcium buildup, or organic staining that regular brushing and chemicals just can’t remove.

Here’s when we’re comfortable going ahead with an acid wash:

• Cooler weather – Highs at or below ~85°F, and ideally not in a heat wave.
• Shade or moderate sun – Early morning or mid-fall/winter is best; harsh midday summer sun is worst.
• Surface condition is good – No major cracks, hollow spots, or areas already failing.
• You understand it’s a “last-resort” clean – Acid removes a thin layer of plaster every time, so it shouldn’t be done every year just for looks.

With Jim, we talked about timing: once it cools down, we’ll drain the pool, protect the surface as we work, neutralize and dispose of the acid correctly, and refill and balance the water so the pool is ready to use again.

Jim’s Second Question: High Chlorine and “Bad” Test Results

While we were talking, Jim mentioned another concern. He had a printout from a pool store water test, and the numbers looked scary. His free chlorine was over 23 ppm, and the report flagged his alkalinity and calcium hardness as “off.”

When he read off the numbers, we walked through them together. His pH was 7.4 — right where we like it — but the test said his total alkalinity was just 13 ppm, way below the “normal” 80–120 ppm range. On paper, it looked like everything needed fixing.

Based on the full picture, here’s what we told him.

How We Tackled His Very High Chlorine

The first issue was that 23 ppm free chlorine. That is very high for a residential pool. The good news is that, in most cases, you don’t need to dump a bunch of chemicals to “fight” it.

Our advice to Jim (and what we usually recommend in this situation):

• Step 1: Remove chlorine tablets – Jim had tabs in his feeder. We told him to take them out and skip tabs for at least a week. No more chlorine until that level comes down.
• Step 2: Run the pump – Keep water circulating so the chlorine distributes evenly and burns off naturally in the sun.
• Step 3: Let time and sunlight work – UV light from the sun will slowly break down the excess chlorine. In our sunny climate, levels usually drop faster than people expect.

What we did not recommend was adding chemical “chlorine removers” right away. In most backyard pools, patience and turning off the chlorine source is safer and easier.

Why We Didn’t Rush to Change His Alkalinity

Jim’s printout showed total alkalinity at 13 ppm, which by the book is far too low. Normally, you’d expect us to say, “Let’s add baking soda or a specialty product to bring that up.”

Instead, we told him something that surprised him: don’t touch the alkalinity yet.

Here’s why:

• His pH was perfect at 7.4, right in the ideal range of 7.2–7.8.
• Raising alkalinity with products like sodium bicarbonate can also push pH higher.
• If we chased that low alkalinity number, we’d likely create a new problem — high pH — and then he’d be adding acid to bring it back down.

So our advice was simple: with pH dead on, leave it alone for now. Retest once the chlorine level comes back into a normal range, and then we can decide whether any adjustment is really needed.

Basic Tips for Balancing Pool Water at Home

If you’re staring at a confusing test report like Jim was, here’s a simple order of operations you can follow:

1. Check chlorine first – If it’s very high, stop adding tabs or liquid chlorine and let it drift down.
2. Look at pH next – Aim for 7.2–7.8. If it’s in range, don’t rush to change other things that might mess it up.
3. Then consider alkalinity – Only adjust if it’s truly low or high and your pH isn’t stable.
4. Calcium hardness and stabilizer (CYA) – Important, but usually slower-moving issues. These are areas where a quick chat or water test with a pro can save you guesswork.

For low pH with low alkalinity, we’ll often recommend soda ash (sodium carbonate) or baking soda products, but we tailor that advice to each pool. That’s why, as we told Jim, it’s often easiest to just bring in a water sample. We can test it, explain what’s going on, and give you measured recommendations instead of guesswork.

DIY vs. Calling a Professional

A lot of homeowners can handle the basics: testing water, turning off chlorine feeders, and adding simple chemicals. We’re always happy to walk you through that and save you a service call when it makes sense.

Here’s when we usually suggest calling a pro like us:

• Anytime you’re draining the pool – Whether it’s for an acid wash, repairs, or a full water replacement, there are real risks to your surface and your pool shell.
• When levels are way out of range – Extremely high chlorine, very low or high pH, or recurring algae blooms.
• If your surface already looks damaged – Scaling, etching, rough spots, or cracks are a sign you need a professional eye.

With Jim, we could solve part of the problem over the phone, and the rest just needed cooler weather and a scheduled visit. That’s the balance we aim for: the right DIY tips when it’s safe and simple, and experienced hands when your pool’s finish or your equipment is on the line.

Need Help Deciding Your Next Step?

If you’re unsure whether it’s safe to acid wash right now, or your water test results look like alphabet soup, you’re not alone. Bring us a water sample, or give us a call with your numbers. We’ll help you decide whether to wait, what to add (or not add), and when it’s time to let a professional step in.

Your pool should be a place to relax — not a science experiment or a construction risk. With the right timing and a little guidance, we’ll keep it that way.