How to Prep Your Pool Before Vacation (So You Don't Come Home to Green)

You’re not going to test and dose your pool from a beach three states away. That’s fine — a pool doesn’t need daily babysitting to survive a week or two. It needs runway. Because a pool turns green while you’re gone for exactly one reason: the free chlorine ran out, and algae took the opening. Everything below is about making sure the chlorine lasts longer than your trip.

First, understand what actually keeps it clear: the reserve

Chlorine doesn’t sit in your water waiting to be used — sunlight burns it off, and swimmers and debris consume it. What makes it last is CYA (cyanuric acid, “stabilizer”): it holds most of your chlorine in reserve and releases it slowly, and it shields it from UV. In Florida sun this is everything — unstabilized chlorine is ~90% gone within two hours (Pentair’s figure). Too little CYA and your chlorine is gone in a day or two; the right amount and it can coast for a week-plus.

So the vacation game is simple: have enough reserve (CYA), fill it up (raise FC), and slow the drain (cut the sun + run the pump).

The 4-step leave-it-safe checklist

1. Balance the water and check your CYA

A day or two before you leave, get everything in range so nothing drifts into trouble: free chlorine, pH, total alkalinity, calcium hardness, and CYA. The one that matters most here is CYA — it’s your chlorine reserve:

• Chlorine pool: CYA 50-80
• Salt pool (SWG): CYA 70-80 (salt pools run higher CYA on purpose)

If your CYA is low, raise it now (granular stabilizer takes 24-72 hours to fully dissolve and register on a test, so don’t leave it to the last hour). If pH or alkalinity is off, fix it before you go — you won’t be here to.

2. Raise free chlorine before you leave — to the top of its range

This is the “top off the tank” step. You want free chlorine high enough that it can drift down for your whole trip without hitting zero. How high depends on your CYA — that’s the whole point of the FC/CYA relationship. Aim for the top of your range for a week; for a trip longer than ~2 weeks, take it all the way to SLAM level to buy maximum runway.

Compute your numbers before you go:

• Target FC band (≈ 11–12% of CYA)
• Minimum FC (≈ 7.5% of CYA)
• Below minimum — algae can grow

Raise it with the right chlorine. If your CYA is already near the top, use liquid chlorine or your salt system to raise FC — not stabilized trichlor tablets, which shove CYA higher every time and can push you out of range (see which chlorine to use). A slow-feed trichlor floater is fine as a steady trickle on a short trip, but don’t rely on it to carry a long one.

3. Keep the pump running — on a timer

Don’t shut the pump off to “save power.” Still water is where algae and cloudiness start, and a salt system makes zero chlorine when the pump is off. A normal daily turnover schedule is plenty — you don’t need 24/7 (see why 24/7 is a myth). If you have a salt cell, bump its output up a notch before you leave so it keeps FC topped off against the sun. If a rare freeze night is possible where you are, enable freeze protection so the pump runs to protect the plumbing.

4. Cut the sun

Sunlight is what drains your reserve fastest, so blocking it is the highest-leverage move:

• A solid or solar cover is the best case — it slashes UV loss and keeps leaves and dust out.
• No cover? Your screen enclosure is already helping — a Florida cage blocks a real share of UV, which is exactly what you want here. (This is the rare time the cage’s shade works fully in your favor.)

How long can you actually leave it?

• Up to ~1-2 weeks: Balanced water + CYA in range + FC raised before you go + pump on a timer + covered/shaded → most pools stay clear on their own.
• ~2-3 weeks: Push FC to SLAM level before leaving and lean on a covered pool or a salt system with output turned up. It’s doable but the margin thins.
• 3+ weeks: Have a neighbor or pool sitter test once a week and add chlorine if it’s low. One person, ten minutes, once a week beats a full green recovery when you’re back and jet-lagged.

If you DO come home to green

Don’t panic and don’t drain it. A green pool is almost always just chlorine that ran out, and it’s fixable with the SLAM process (raise FC to the SLAM level for your CYA and hold it there until the water clears) — walk through it in my pool is green. The come-home-to-green is preventable, but it’s not a disaster if it happens.

Bottom line: you don’t babysit a pool through a vacation, you set it up to coast. Balance it, make sure CYA is holding a real chlorine reserve, raise free chlorine before you walk out the door, keep the pump on a timer, and cut the sun. Do that and the water’s clear when you get back — no swamp, no re-do.