Your first week with a new hot tub is the most important one. Get the chemistry right from the start, build a daily testing habit, and you will rarely have a water problem worth worrying about. Fill the tub, balance alkalinity first (target 80-120 ppm), then pH (7.4-7.6), then calcium hardness (150-250 ppm), add sanitizer, shock, and test every single day for seven days. That is the whole frame. Everything below fills in the details.
A lot of new hot tub owners get a little overwhelmed in the first few days and either over-treat the water or stop testing because nothing looks wrong. Both create problems. Over-treating throws your balance off. Under-testing means you miss a shift before it becomes cloudy water or a rash. The good news: the first week is also the easiest time to get ahead of things, because you are starting from scratch with fresh water.
What to Do Before You Fill the Tub
Before you even run the hose, do a quick visual inspection of the shell, jets, and filter housing. Make sure the filter cartridge is seated properly. If the tub sat in a warehouse or on a showroom floor, run a line flush product through the plumbing before filling – even new tubs can have dust, residue, or manufacturing oils in the lines that will cause foam in your first soak.
Use a garden hose filter if your source water is high in metals or minerals. Copper and iron in fill water can stain your shell and throw off your chemistry before you even start. A simple inline hose filter costs under $20 and removes most of the problem minerals. If you know your area has hard water (above 200 ppm calcium), this step matters even more.
Day 1: Fill and First Balance
Fill the tub through the filter housing or skimmer intake – not directly into the shell. This prevents air locks in the jets. Once filled, turn the heat on but do not get in yet. Let the water circulate for 30 minutes, then test your baseline numbers before adding anything.
Add chemicals in this order, waiting at least 30 minutes between each with jets running:
- Metal sequestrant – if your source water has metals, add this first and let it circulate for an hour before anything else.
- Total alkalinity adjuster – get TA to 80-120 ppm. Use sodium bicarbonate to raise it, muriatic acid or a dry acid to lower it.
- pH adjuster – target 7.4-7.6. pH down (sodium bisulfate) or pH up (sodium carbonate) depending on where you land.
- Calcium hardness increaser – target 150-250 ppm. If your fill water is already in range, skip this or add a small amount.
- Sanitizer – add your chlorine or bromine according to the label for your tub’s volume. For bromine, you need to establish a bromide bank first before shocking.
Finish Day 1 by shocking the water. Use a non-chlorine shock (potassium monopersulfate) or a chlorine shock at startup dose – 2 oz per 250 gallons is a common starting point for chlorine shock. Let it circulate for at least 30 minutes with the cover off before closing up for the night. Do not soak yet.
Days 2 Through 4: Test Every Day and Let It Settle
New water takes a few days to stabilize. pH in particular tends to drift high in fresh water as dissolved CO2 off-gasses. Test every morning before anyone gets in, and record your numbers. You are looking for: free sanitizer at 3-5 ppm for chlorine, or 2-4 ppm for bromine; pH at 7.4-7.6; and alkalinity still in the 80-120 ppm range.
If pH keeps climbing back above 7.8 day after day, that is normal for the first week and will usually stabilize on its own. Add a small dose of pH decreaser (no more than 1 oz per 300 gallons at a time), retest after 30 minutes, and repeat if needed. Avoid dumping large amounts in at once – you will overshoot and then spend two days correcting back upward.
This is also a good stretch to get familiar with how you are testing your water – strip, liquid, or digital – because the accuracy of your routine depends on how well you read the results. Test strips are fine for daily spot-checks; a liquid drop test kit gives you a more precise reading when something seems off.
When Can You Actually Soak?
You can get in once your water is balanced, your sanitizer is in the correct range, and the shock has had time to dissipate. For most people that is late Day 1 or sometime on Day 2. If you shocked with chlorine, wait until free chlorine drops below 5 ppm before soaking. If you used non-chlorine shock, 20-30 minutes with jets running is enough. Test before you get in – not after.
Do not skip the test because the water looks clear and smells fine. Sanitizer levels and pH are invisible. A tub with pH at 8.2 and low chlorine will feel fine for a few minutes and then irritate your eyes and skin. This is the single most common first-week mistake.
Days 5 Through 7: Build the Habit
By the end of the first week, your water should be stable and you should have a feel for how fast your tub burns through sanitizer. Now you are building the routine that will carry you for the next three months until your first water change.
The basic rhythm for most hot tub owners is: test every 2-3 days, add sanitizer as needed to hold your target level, and do a light shock once a week after heavy use or once every two weeks for lighter use. AquaDoc makes a weekly maintenance kit that bundles these steps into a simple system for new tub owners who want a less guesswork approach.
Rinse your filter cartridge with a hose at the end of Week 1. A brand-new filter does not need a chemical soak yet, but rinsing off the initial debris now helps it flow properly and keeps your water cleaner from the start. Plan a full chemical filter soak at the 30-day mark.
Common First-Week Mistakes Worth Avoiding
- Adding chemicals in the wrong order. Always fix alkalinity before pH, and pH before sanitizer. Adjusting them out of sequence means you end up chasing your tail.
- Not testing before each soak. Two days without testing is fine once you know your tub. In Week 1, test daily.
- Running the heater without circulation. Your heater needs water moving through it. Make sure jets or the circulation pump are running when heating, especially in cooler weather.
- Leaving the cover on during chemical additions. Always add chemicals with the cover off and jets running so they dissolve and circulate properly, not just sit on the surface.
- Inviting people over on Day 1. Heavy bather load in fresh water before it is fully balanced is a fast path to foam and cloudy water. Get through Day 3 before the guests arrive.
What Good Looks Like After Week One
At the end of seven days, you should have clear water, a sanitizer level you can maintain consistently, pH that is not swinging more than 0.2 per day, and a basic routine you actually understand. You will not have everything perfectly dialed yet – that takes a few weeks – but you will have a stable foundation. The problems that send new owners to forums in a panic (foam, cloudy water, skin irritation) almost always trace back to skipping one of the early setup steps or stopping testing too soon. Stick with the daily checks for one full week and you will earn the right to relax the schedule.
Frequently Asked Questions
What chemicals do I need to add when I first fill a hot tub?
Start with a metal sequestrant if needed, then balance total alkalinity (80-120 ppm), then pH (7.4-7.6), then calcium hardness (150-250 ppm), and finally add your sanitizer. Add them in that order and wait at least 30 minutes between each, with jets running.
How soon can I get in a new hot tub after adding chemicals?
Wait at least 30 minutes after adding balancing chemicals, and at least 15-20 minutes after adding sanitizer, with jets running. If you shocked the water with chlorine, wait until free chlorine drops below 5 ppm before soaking.
How often should I test my hot tub water in the first week?
Test every day for the first week. New water is unstable and levels shift fast, especially pH and sanitizer. Daily testing for the first 7 days lets you catch problems before they turn into cloudy water or skin irritation.
What should total alkalinity be in a hot tub?
Total alkalinity should be between 80 and 120 ppm in a hot tub. Getting this right first makes pH much easier to control, since alkalinity acts as a chemical buffer that keeps pH from swinging up and down.
Do I need to shock my hot tub before the first use?
Yes. Add a startup shock dose after balancing your water chemistry and before your first soak. This clears any contaminants introduced during filling and establishes a clean sanitizer baseline to work from.