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How long to run the pump after you add something
A chemical only does its job once it is mixed through the whole pool. Until then the spot where you poured is strong and the far end has not seen it. The pump is what mixes it, so the rule is short: the pump is on when anything goes in, and it stays on at least until the retest time in your plan.
Nothing to do but leave it on
When this applies
Any plan that asks you to add something.
A dose that seemed to do nothing. A short pump run is one of the commonest reasons.
- 1Turn the pump on before you pourStart the pump and check that water is moving at the returns. Then add the product the way the plan says: liquids poured slowly near a return jet or into the deep end, powders broadcast or dissolved in a bucket first. Never pour into the skimmer. The one exception is stabilizer in a sock in the skimmer basket, when the plan says so.Moving water carries the product away from where it lands. Poured into still water, acid sinks and sits on the floor, and that strong patch can etch plaster or bleach a liner.
- 2Leave it on until the retest timeEvery dose in your plan comes with a retest time, and each product’s steps say how long to run the pump: a few hours for acid, longer for soda ash, baking soda and calcium, and all night for a shock. Keep the pump running at least that long.The retest time is how long the engine expects the product to need to mix and act. Testing sooner reads a half-mixed pool, and adding more off a half-mixed reading is the most common way people overshoot.
- 3All night after a shock, all day and night during a clearing holdA shock goes in in the evening and the pump runs through the night. A clearing hold for green water runs the filter around the clock until the hold is finished.A shock level has to reach every corner, including behind the ladder and the steps, where algae and used-up chlorine hide. At night the sun is not burning it off while it works.
- 4Aim the returns downPoint the return jets down and slightly to one side, so the water turns over along the floor instead of skimming the surface. If the plan asks you to aerate to raise pH, that is the one time they point up.Returns aimed at the surface mix only the top of the pool. Aimed down, they move the whole body of water.
- 5Stabilizer and salt are slow: retest later, do not add moreStabilizer can take up to a week to dissolve. Leave it in its sock and do not backwash for about two days after adding it. Salt needs about a day before a reading means anything. Your plan’s retest time already allows for this.A low stabilizer reading the day after adding it is usually stabilizer still sitting in the skimmer, not a dose that failed. Adding more is how stabilizer ends up too high, and only draining brings it back down.
When to call a professional
- The pump will not prime, hums without turning, or trips the breaker. Hold off on chemicals until the water is moving again: a dose added with no circulation sits in one place.
Your everyday pump schedule is a separate question. If chlorine keeps disappearing faster than it should, the app’s follow-up check names a short daily pump run as one of the causes to rule out, alongside a dirty filter and full baskets.
Where this comes from
- packages/chemistry-engine/src/content/chemicalGuidance.ts: how each product goes in and how long the pump runs after it.
- packages/chemistry-engine/src/followUp/rankCauses.ts: a short pump run as a cause of chlorine that will not hold.
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