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Dolphin Pool & Spa

Hot Tub Season Never Ended: Late-Summer Spa Chemistry Check-In

Thursday, August 20, 2026

Hot tub on a Minnesota deck in late summer evening light

Images are AI generated and do not depict an actual pool or Dolphin Pool & Spa location.

Once the pool opens, the hot tub tends to slide down the priority list. That's a mistake. Your spa runs hot, runs small, and runs all year. Late summer is a good time to give it a real look before fall guests start using it more.

1 Small Volume, Big Swings

A hot tub holds a fraction of the water your pool does. That means chemicals work fast, but water balance also drifts fast. A hot afternoon, a few extra guests, or one skipped test and your numbers can move more than you'd expect. Test more often than you think you need to.

Tip: Test your spa water at least twice a week in late summer. If you're not sure where your numbers stand, bring a sample in. Water testing is $7, or free with a $50 or more chemical purchase.

2 Where Your Numbers Should Sit

Spa targets run a bit different from pool targets. Here's what to check for:

Reading Spa Target Range Pool Target Range
pH 7.4–7.6 7.4–7.6
Total Alkalinity 80–120 ppm 100–150 ppm
Sanitizer (Chlorine or Bromine) 3–5 ppm 1–3 ppm
Calcium Hardness 150–250 ppm 200–400 ppm

Set your spa side by side with your pool and the difference is clear. Sanitizer runs higher in a spa because heat burns through it faster. Calcium hardness runs lower, since too much in a small, hot volume speeds up scale on your heater and jets.

3 Heat Eats Sanitizer

Hot water burns through sanitizer faster than cool water. On a hot week, your bromine or chlorine level can fall even if nobody's used the tub. Check it more often in August than you would in January.

If your levels keep dropping fast, shock the water. BioGuard shock products need just 15 minutes before you can get back in — not the 4 hours some generic shocks require. That's a real difference when guests are waiting on the deck.

4 Guests Add Up Fast

Late summer means more cookouts, more visitors, more time in the tub. Each person who gets in brings body oils, lotion, and sweat with them. In a small volume, that load shows up quickly as cloudy water or a musty smell.

After a Full Tub

  • Test sanitizer and pH the next morning
  • Run the jets to circulate fresh water
  • Shock if the water looks hazy

Before a Party

  • Confirm sanitizer sits in range
  • Ask guests to rinse off first
  • Keep the cover off between uses to vent heat

5 Don't Skip the Filter

A dirty spa filter can't keep up with heavy summer use. Rinse it every week during a busy stretch, and give it a real soak in filter cleaner once a month. A clean filter means your sanitizer works on the water, not on debris.

Don't want to deal with it yourself? Bring your filter in. We give it a full soak in a muriatic acid bath to strip out oils, scale, and buildup that rinsing alone won't touch. It's $30 per cartridge, or $150 for a full Sta-Rite pool filter set.

Heads up: Foam on the surface usually means body products or old, worn-out water — not a sanitizer problem. If foam keeps coming back after you drain and refill, bring a water sample in so we can check what's causing it.

Your hot tub works hard in every season, including this one. A few extra minutes of testing now keeps the water clear and the equipment happy through fall.

Not sure where your spa water stands? Bring in a sample and we'll test it and walk you through what to add. From chemistry to equipment, we make pool ownership a joy!

Call Us Now — 763-542-9000

Your Happy Dolphin Pool & Spa Team

3405 Hwy 169 N, Plymouth, MN 55441 | 763-542-9000