You just got your first hot tub. The cover is on, the water is full, and you’re staring at a bag of chemicals wondering if you’re about to turn your backyard into a science experiment. Here’s the thing most new owners don’t realize: week one sets the foundation for everything. Get it right and you’ll spend five minutes a week keeping the water clear. Get it wrong and you’ll spend the next month chasing problems you don’t fully understand yet.
This is a day-by-day walkthrough of what to actually do that first week, with real numbers and the mistakes you’ll want to skip.
Day 1: Fill It Right From the Start
Before you add a single chemical, filter your fill water. Run your garden hose through an inline pre-filter before it goes into the tub. Hot tubs hold 300 to 500 gallons – a small volume compared to a pool – so whatever metals or minerals are in your tap water get concentrated fast. Copper and iron cause staining, and by the time you see it, it’s already a problem.
Fill the tub through the filter housing, not just over the edge. This helps you avoid air pockets in the plumbing lines, which can cause your jets to run dry and hum when you first fire up the heater.
Once filled, turn everything on and let it circulate for at least 30 minutes before you test or add anything. The water needs to mix and the equipment needs to prove it’s working before you start dosing.
Day 1 (Evening): Get Your Baseline Chemistry
Test strips are fine for quick daily checks, but on day one, use a proper liquid test kit or take a water sample to your local pool store. You need accurate numbers, not approximations, because everything you add this week is based on where you’re starting from.
Here are the targets you’re aiming for:
- Total Alkalinity: 80 to 120 ppm
- pH: 7.4 to 7.6
- Calcium Hardness: 150 to 250 ppm
- Sanitizer (chlorine): 3 to 5 ppm free chlorine, or follow your bromine kit instructions
- Total Dissolved Solids (TDS): under 1500 ppm above your source water baseline
Always adjust alkalinity first, then pH, then sanitizer. This order matters because alkalinity acts as a buffer for pH. If you try to fix pH when your alkalinity is off, you’ll be chasing your tail for days.
Day 2: Balance and Shock
Now you adjust based on what you found yesterday. Add alkalinity increaser or decreaser in small doses – for a 400-gallon tub, a quarter-pound adjustment is meaningful. Don’t try to correct 50 ppm of alkalinity in one shot. Overshoot, and you’re adding more chemicals to correct the correction.
Once alkalinity is dialed in, adjust pH. Dry acid (sodium bisulfate) brings pH down, sodium carbonate brings it up. Add small amounts, circulate for 15 to 20 minutes, then retest before adding more.
After pH is stable, do your startup shock. Use a non-chlorine shock or a chlorine shock at a higher dose – typically 2 to 4 times your normal sanitizer dose – to oxidize anything that came in with the fill water. Let the tub run with the cover off for at least 20 to 30 minutes after shocking so off-gassing can happen. Getting in too soon after shocking is one of the most common first-week mistakes.
Day 3 and 4: Let It Settle, Then Test Again
This is the part where new owners get jumpy. The water might look slightly cloudy or have a faint smell – that’s often just residual oxidation from the startup shock working its way through. Resist the urge to dump in clarifier or more chemicals.
Test on day three and day four. You’re looking for pH and sanitizer levels specifically. At this point in week one, you haven’t used the tub much yet, so the chemistry should be relatively stable. If your pH is creeping up, that’s normal for fresh water – outgassing of carbon dioxide tends to raise pH in new fills. Small doses of pH decreaser will handle it.
If your chlorine is sitting below 2 ppm, add a maintenance dose. For chlorine tablets in a floating dispenser, a single 1-inch tablet in a 400-gallon spa typically holds levels reasonably steady, but tablets alone are not a substitute for regular shocking.
Day 5: Your First Real Soak
Check your chemistry before you get in. pH in range, sanitizer above 3 ppm, and you’re good. This is the first time you’ll notice what the water actually feels like when it’s balanced – no eye irritation, no strong chemical smell, no itchy skin afterward. That’s what you’re trying to maintain every week from here on out.
After your soak, test again. Bather load – even one person for 20 minutes – burns through sanitizer faster than you’d expect. Body oils, lotions, and sweat all consume chlorine or bromine. You may need to add a small dose after each use. AquaDoc makes a chlorine-based spa shock that a lot of owners use for this kind of post-soak oxidation, because it handles the organic load without spiking your levels too aggressively.
Day 6: Clean the Filter
Your filter has been running all week. On new fills especially, it picks up metals, oils, and debris from the fill water. Rinse it with a garden hose – spray each pleat individually, top to bottom. This is not the same as a deep chemical soak, which you’ll do monthly, but it makes a real difference in week one.
Don’t put a wet filter back in and immediately replace the cover. Let it drain for a few minutes first. A clogged or poorly rinsed filter is one of the top causes of cloudy water in new setups.
Day 7: Set Your Weekly Habits
By the end of week one, you should have a feel for how fast your sanitizer drops, how stable your pH is, and how your tub responds to use. That knowledge is worth more than any schedule someone hands you, because every tub is different depending on your source water, how often you use it, and how many people are soaking.
Here’s a simple weekly checklist to take into week two and beyond:
- Test pH and sanitizer 2 to 3 times per week
- Shock after every heavy use session, or once a week minimum
- Rinse the filter every 2 weeks
- Deep-soak the filter in filter cleaner once a month
- Test total alkalinity and calcium hardness once a month
- Drain and refill every 3 to 4 months – hot tubs concentrate everything over time
The biggest mistake new owners make is treating hot tub chemistry like a set-it-and-forget-it situation. It’s not a pool. The water volume is small, the temperature is high, and things change fast. But if you test consistently and make small corrections early, you’ll almost never have a real crisis. Week one is the hardest part. After that, you’re just maintaining something that’s already in balance.