ChlorBenchPool volume and chemical doses worked out, not guessed.

How much cal-hypo for a 16 × 32 ft oval pool to raise chlorine 1 ppm

Cal-hypo (65%) to add
3.3oz
raises free chlorine 1 ppm in 16,545 gallons — 32 × 16 ft oval
Sectionavg 5.5 ft5 ft6 ft16,545gallons32 × 16 ft oval3.3 ozCal-hypo (65%)
Dose0.09 kg3.3oz
Pool volume32 × 16 ft oval, 5–6 ft deep (avg 5.5 ft)16,545gallons
Volume in ft³× 7.48052 gal per ft³2,212ft³
Target risefree chlorine1 ppm
What else it addsadds about 0.8 ppm calcium hardness per ppm of chlorine
— Same job, other products —
Dichlor (56%)adds about 0.9 ppm cyanuric acid per ppm of chlorine3.8oz
Trichlor (90%)adds about 0.6 ppm cyanuric acid per ppm, and is strongly acidic2.5oz
Liquid chlorine (12.5%)adds nothing but salt — raises pH slightly17.7fl oz
Household bleach (8.25%)same chemistry as liquid chlorine, weaker26.5fl oz
Pool size
16 × 32 ft oval
Shallow end
5 ft
Deep end
6 ft
Raise by
1 ppm
Product
cal-hypo

Volume first — everything else is volume × a constant

A 16 × 32 ft oval pool running 5 to 6 ft deep holds 16,545 gallons. Average depth is 5.5 ft, and 2,212 cubic feet × 7.48 gives the gallons.

Get this wrong by a fifth and every chemical you add for the life of the pool is wrong by a fifth. Measure the pool. The brochure figure is for the model, not for what got built.

The dose

3.3 oz of cal-hypo raises free chlorine by 1 ppm.

What else it adds — and this is the part that matters

cal-hypo adds about 0.8 ppm calcium hardness per ppm of chlorine.

That is not a footnote. Cal-hypo builds calcium hardness until it scales the tile line and the heater. Dichlor and trichlor build cyanuric acid, and above about 50 ppm CYA holds chlorine so tightly that the chlorine stops killing anything — and the only cure is draining and refilling. Liquid chlorine adds nothing but salt and a little pH.

Rotating products across a season, rather than using one, is how you avoid ending up with water that has to be replaced to be fixed.

How to add it

Pump running. Slowly, at the deep end or through the skimmer. Undissolved granules resting on a vinyl liner bleach it permanently and that damage does not come out.

Test after four hours of circulation. A reading taken straight after dosing tells you about the water beside the return jet, not about the pool.

Notes

  • **Volume first, and everything else follows.** A 32 × 16 ft oval pool at 5.5 ft average depth holds 16,545 gallons. Every dose on this page and every dose you will ever add is that number × a constant — get it wrong by a fifth and every chemical for the life of the pool is wrong by a fifth. Measure the pool; do not trust the brochure.
  • Average depth here is (5 + 6) ÷ 2 = 5.5 ft. That is exact for a pool with a straight slope. Pools with a bench, a spa step or a flat shallow section that drops off need the sections worked out separately and added.
  • **Cal-hypo (65%) adds more than chlorine.** It adds about 0.8 ppm calcium hardness per ppm of chlorine. In hard-water areas this is what scales the tile line and the heater. Rotating products, rather than using one all season, is how you avoid ending up with water that needs draining to fix.
  • Because this product adds no stabilizer, chlorine in an outdoor pool will burn off fast in sun unless CYA is already in the 30–50 ppm range. Test it before assuming the dose is not working.
  • Add it with the pump running, and add it slowly at the deep end or through the skimmer. Undissolved granules sitting on a vinyl liner bleach it permanently.
  • Test after four hours of circulation, not immediately. A reading taken straight after dosing tells you about the water beside the return, not about the pool.

Nearby sizes

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