Dose chlorine, pH, alkalinity, hardness, stabiliser, and salt from your current readings to your targets, in the order the adjustments should be made, with a saturation index for the water as a whole.
Change the inputs that matter to your decision. Optional assumptions stay collapsed until you need them.
Every dose is proportional to volume, so this is the number that matters most.
Alkalinity is set first because it buffers pH, and each adjustment moves the other.
5 adjustments for 20,000 gallons, in the order they should be made.
The water is close to saturation, which is where it neither dissolves nor deposits calcium. Work down the list in order, letting the water turn over between steps, and retest before the next one. Never mix two products in the same container or add them at the same point in the pool.
| 1. Total alkalinity | 8.4 lb70 ppm → 100 ppm · Sodium bicarbonate (baking soda). Raises pH slightly as well. Add over the return, brush, and retest after a full turnover. |
|---|---|
| 2. pH | 16.9 fl oz7.8 → 7.5 · Muriatic acid (31.45%). Add to water, never water to acid, and keep it away from chlorine products. This also drops total alkalinity by about 3 ppm, which is why alkalinity is set first. |
| 3. Calcium hardness | 16.8 lb180 ppm → 250 ppm · Calcium chloride (77% flake). Dissolves exothermically. Add slowly to a bucket of water first, never the reverse. |
| 4. Cyanuric acid | 3.3 lb20 ppm → 40 ppm · Cyanuric acid (stabiliser). Dissolves slowly. Add through the skimmer sock and allow several days before retesting. |
| 5. Free chlorine | 43.8 fl oz0.5 ppm → 3.0 ppm · Liquid chlorine (12.5% sodium hypochlorite). Adds no stabiliser and no calcium; loses strength in storage. Add with the pump running and keep everyone out until it reads back in range. |
Doses are derived from the mass of water in the pool and the strength of the product named, not from a fixed per-ten-thousand-gallon table, so changing the product changes the quantity. The pH step is modelled through the carbonate buffer, which is why alkalinity changes the acid or soda ash required. Add roughly three quarters of any dose, let the pool turn over, and retest before adding the rest.
Practical notes about the inputs, assumptions, and result.
Because each one moves the others. Alkalinity buffers pH, so setting pH before alkalinity means doing it twice. Acid lowers alkalinity as well as pH; soda ash raises both. Chlorine goes last because the pump running and the water turning over during the earlier steps will consume some of it.
Because the dose is worked out from the available chlorine in the product you are actually holding. One ppm in 10,000 gallons is about 0.083 lb of available chlorine; that is 1.8 oz of 73% cal-hypo, 2.4 oz of 56% dichlor, or roughly 9 fl oz of 12.5% liquid. A fixed table cannot express that.
Alkalinity is the water's resistance to a pH change, so a pool at 140 ppm needs considerably more acid to drop the same 0.5 pH than one at 60 ppm. The pH step here is modelled through the carbonate buffer rather than a flat ounces-per-tenth rule, which is why the number moves when you change alkalinity.
You cannot, with any additive. Neither is consumed and nothing removes them, so the only route down is replacing water. The tool reports the share of the pool to drain and refill rather than inventing a product dose.
Whether the water is in balance with calcium carbonate. Below about −0.3 it is aggressive and will pull calcium out of plaster, grout, and stone; above about +0.3 it deposits scale on surfaces, in the heater, and on a salt cell. It combines pH, temperature, calcium, and alkalinity, which is why the four have to be judged together rather than one at a time.
No. Add about three quarters, let the pool turn over fully, and retest before adding the rest. Overshooting is far more work to fix than undershooting, especially with pH and stabiliser. And never combine two products in a bucket or add them at the same point in the pool.
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