Safest way to put in chemicals in your pool (or spa) – Sutro

Before adding chemicals

Skim the surface of the pool and remove any debris or floating toys
Make sure everyone is out of the water and knows you're adding chemicals to the pool
Before handling any chemicals, make sure your hands are dry or gloves are dry.
Unless stated otherwise by the chemical manufacturer, circulate the water to mix and distribute the chemicals in the water.

Check the side of the container to confirm the % active chlorine. For store bought bleach, this is usually around 8% depending on how long it has been on the shelf.
Do not use scented or splashless bleach in your pool or spa.
Check the side of the container for volume markers, this will help you know how much you have added. Remember where you started if it is not a new bottle.
Careful to prevent splashing, gently pour the liquid chlorine around the perimeter of the pool or spa. Check the level on the container to make sure you've added enough.
After all of the chlorine is added, brush the inside wall of the pool to finish mixing. For spas, turn on the jets and aerators to mix the chlorine into the lines as well.

Chlorine and bromine tablets are usually dissolved in a floating dispenser and sometimes in an in-line chlorinator.
If the tablet is wrapped in plastic, remove the plastic and lay flat inside the dispenser. If the tablet is wrapped in a dissolvable wrapper, you may place the tablet with the wrapper in the floating dispenser. Check with in-line chlorinator manufacturers for specific instructions on dissolvable wrappers.
Lock the top of the floating dispenser and check the bottom for adjustable slots. These can increase or decrease the flow inside the dispenser to manage how fast the chlorine dissolves.
Gently place the chlorine dispenser back into the pool.
Bromine tablets do not start working immediately unless the water has a bromine reserve. You can quickly establish a bromine reserve using sodium bromide, usually sold in small packets.

If new, check the package to confirm the chlorine type and % active chlorine. There are many types of chlorine that are similarly named, so it doesn't hurt to check.
For 1 lb bags measurements can be approximated by the bag for pounds and quarter pounds. If the chlorine is a bulk bucket, having a dedicated scoop or measuring cup could help.
Remember, always keep chemicals dry until you add them to your pool or spa. If a measuring cup or scoop is used, always use it for the same chemical. Don't use the same scoop for different chemicals.
Broadcast or spread the chlorine on the water surface as evenly as possible. If any clumps occur, use a pool brush or surface skimmer to distribute the clumps. You don't want large clumps to slowly dissolve on the surface of the pool or spa.

Measure with a dedicated measuring cup or scoop.
Broadcast or spread the pH up across the surface of the water.
If any clumps develop, distribute them with a pool brush or surface skimmer. You don' want large clumps slowly dissolving on the surface of the pool or spa.

Measure with a dedicated measuring cup or scoop.
Broadcast or spread the pH down across the surface of the water.
If any clumps develop, distribute them with a pool brush or surface skimmer. You don' want large clumps slowly dissolving on the surface of the pool or spa.

Check the side of the container to confirm the % of acid. Muriatic acid is commonly sold in 15-30% increments.
Check the side of the container for volume markers, this will help you know how much you have added. Remember where you started if it is not a new bottle.
Careful to prevent splashing, gently pour the muriatic acid around the perimeter of the pool or spa. Check the level on the container to make sure you've added enough.
After the muriatic acid is added, brush the inside wall of the pool to finish mixing.
It is important to carefully walk the perimeter and pour muriatic acid gently. You do not want to splash and you do not want a pocket of acid to develop at the bottom of the pool or spa.

Measure with a dedicated measuring cup or scoop.
Broadcast or spread the alkalinity up across the surface of the water.
If any clumps develop, distribute them with a pool brush or surface skimmer. You don' want large clumps slowly dissolving on the surface of the pool or spa.

Cyanuric acid or stabilizer is contained in many granular and tablet-based chlorines. This is not a reliable way to quickly increase the stabilizer in the water, but do keep in mind these will slowly raise the concentration.
Cyanuric acid dissolves slowly and is an acid, so it is best not to allow granules or clumps to slowly dissolve directly in contact with the pool liner.
Some guides mention using the skimmer directly but this could potentially damage your filter or pump.
The most reliable way to add stabilizer to your water is to dissolve the recommended dose into a large bucket of pool water. Then carefully pour the contents around the perimeter of the pool.
Another method to more slowly add cyanuric acid through the skimmer basket is to use a tube sock, not one you want to use again. Add the cyanuric acid to the sock and tie off the end. This can be placed inside the basket to slowly dissolve. This requires to remember to take the sock out, you don't want it somehow making it past the skimmer basket.