Your first week with a new hot tub is the most important week of ownership. Fill it right, balance it in the correct order, shock it before anyone gets in, and run the jets and filter properly – and you set yourself up for easy maintenance for years. Skip any of those steps and you’ll be chasing cloudy water, itchy skin, or foam before the end of the month. Here’s what to do, day by day, in plain terms.
Why the First Fill Sets the Tone
Fresh tap water is not ready for a hot tub. It has unknown alkalinity, pH that varies by region, minerals that may be too low or too high, and zero sanitizer. Before you ever turn the heater on or step a foot in, you need to know what you’re starting with. Fill the tub completely with the jets off and the cover open, then run your first water test. A liquid test kit gives you more accurate readings than strips for this initial baseline – but either works better than guessing.
Your local water source matters a lot here. If you’re on well water, you may have high iron or calcium. If you’re on city water, you might have chloramines or high alkalinity from treatment. Whatever you’re working with, the fill water chemistry is your starting point, not your end point.
Day One: Balance in the Right Order
Balancing hot tub water has a correct sequence. Do it out of order and you’ll waste chemicals and time. Follow this order every single time:
- Total alkalinity first. Target 80 to 120 ppm. Alkalinity buffers pH, so if it’s off, your pH will swing all over the place no matter what you add. Use an alkalinity increaser if you’re low (most people are on first fill).
- pH second. Target 7.4 to 7.6. Low pH corrodes equipment and irritates skin. High pH makes sanitizer ineffective and causes scaling. Use pH Up or pH Down in small doses, then retest after 30 minutes of circulation.
- Calcium hardness third. Target 150 to 250 ppm for most hot tubs. Soft water is corrosive – it pulls calcium from your heater, shell, and jets. Hard water scales up your equipment. If you’re low, add a calcium hardness increaser.
- Sanitizer last. Add your chlorine or bromine only after the other parameters are balanced. Sanitizer efficiency depends heavily on pH, so getting pH right first means you’ll use less sanitizer and it’ll work better.
After adding each chemical, run the jets for 15 to 20 minutes to circulate before retesting. Don’t rush this step – it’s the difference between accurate results and phantom readings.
Day One (Evening): The Pre-Soak Shock
Before anyone uses the tub for the first time, shock it. Even a brand-new hot tub can have residue from manufacturing, shipping, or the fill hose. Use a chlorine-based shock at roughly 1 oz per 100 gallons for an initial dose, then let the tub circulate with the cover off for at least an hour. Retest sanitizer levels before getting in. Chlorine should read between 3 and 5 ppm if you’re using chlorine as your primary sanitizer. If you’re setting up a bromine system, establish your bromine bank first per the manufacturer’s instructions before shocking.
How Do I Know When It’s Safe to Soak?
Before your first soak, all four of these should be in range:
- Total alkalinity: 80 to 120 ppm
- pH: 7.4 to 7.6
- Calcium hardness: 150 to 250 ppm
- Free chlorine: 3 to 5 ppm (or bromine: 3 to 5 ppm)
If all four are in range, you’re good. If any one is off, fix it before soaking. The most common reason new hot tub owners end up with itchy skin or cloudy water in week one is getting in before chemistry is fully dialed.
Days Two Through Seven: Build Your Testing Habit
Test your water every single day during the first week. Fresh fill water fluctuates more than established water – pH and sanitizer especially can swing quickly as the tub heats up and the system stabilizes. Daily testing in week one lets you spot drift early and correct small problems before they compound.
A simple daily checklist for the first week:
- Test pH, alkalinity, and sanitizer level
- Top off sanitizer if it’s dropped below 3 ppm
- Rinse your filter once mid-week (a quick hose-down, not a full chemical soak)
- Check that your jets and circulation are running for at least one filter cycle per day (typically 2 to 4 hours depending on your system)
- Wipe the waterline with a hot tub surface cleaner if you see any early film building up
AquaDoc makes a simple 5-in-1 hot tub test strip that covers all the basics for this daily check – it’s the kind of thing that’s useful to keep by the tub in week one so testing doesn’t feel like a chore.
After your first soak with other people in the tub, add a small maintenance dose of sanitizer and retest 30 minutes later. Bathers introduce organics (body oils, lotions, sweat) that burn through sanitizer fast. The pool professionals at Pool Troopers note that the same principle applies to any small-volume treated water – bather load is one of the biggest variables in how fast your chemistry shifts.
What Most New Owners Get Wrong in Week One
The most common mistake is skipping alkalinity and jumping straight to pH. If your alkalinity is off, your pH will drift back within hours of you adjusting it. Fix alkalinity first and pH becomes dramatically easier to hold.
The second common mistake is adding chemicals too fast. Dump a full dose of pH Down and then immediately retest – you’ll almost always overshoot. Add half a dose, circulate for 20 minutes, retest, then add more if needed. Hot tub water is only 250 to 500 gallons – small volumes respond fast to chemicals.
Third: leaving the cover on while chemicals are dissolving. Circulation with the cover off lets gases escape and gives you accurate test readings. Cover the tub after everything has had time to mix in fully.
Filter and Cover: Two Things That Pay Off All Year
Your filter is doing most of the work to keep water clear, especially in week one when your water is still stabilizing. Rinse it with a hose after the first few soaks – don’t wait for the scheduled monthly cleaning. A clogged filter in week one can look like a chemistry problem when it’s actually just a dirty filter restricting flow.
Your cover is your biggest energy saver. Keep it on whenever the tub isn’t in use, especially in that first week while the water is heating and holding temperature. A well-fitting cover also reduces evaporation, which means less chemical drift and fewer top-offs. The Pool and Hot Tub Alliance recommends covers as one of the top ways to reduce both energy use and chemical consumption over a tub’s lifetime.
Frequently Asked Questions
How soon can I use my hot tub after filling it?
Wait until your pH is between 7.4 and 7.6, alkalinity is between 80 and 120 ppm, and sanitizer is at the correct level before soaking. That usually takes 24 to 48 hours after the initial fill and chemical additions.
What chemicals do I need for a brand new hot tub?
You need a pH increaser or decreaser, an alkalinity increaser, calcium hardness increaser, and a sanitizer (chlorine or bromine). A startup shock dose is also recommended before first use.
How often should I test my hot tub water in the first week?
Test daily during the first week. Fresh fill water fluctuates more than established water, and catching a drift early saves you from a full chemistry reset.
Do I need to shock a new hot tub before the first use?
Yes. Even brand-new tubs can have residue from manufacturing or shipping. Shock the water with a chlorine shock dose after balancing your alkalinity and pH, and before your first soak.
What should hot tub alkalinity be set to first?
Set total alkalinity to 80 to 120 ppm before adjusting pH. Alkalinity acts as a buffer for pH, so getting it right first makes pH much easier to stabilize.
The first week feels like a lot. It’s not – it’s just unfamiliar. Once you’ve run through the balance sequence once and seen how your tub responds, it becomes muscle memory. Get the chemistry right before that first soak, test every day for seven days, and you’ll head into month two with clean water, a working filter, and a tub you actually trust.