DIY
DIY · green pool rescue

Your pool went green. Here’s the playbook.

The SLAM method — Shock, Level, And Maintain — is what actually works. 3 to 7 days if you commit to it.

Video walkthrough coming soon.

Why pools go green

It’s never just “low chlorine.” A pool goes green when three things line up: low or ineffective chlorine, warm water, and organic contaminants (leaves, pollen, rain washoff). The chlorine problem is usually one of:

  • You literally ran out of tabs (easy fix).
  • Your CYA is too high and it’s locking your chlorine (see chemistry 101).
  • Phosphates from fertilizer/organics are feeding algae faster than chlorine can kill it.
  • A recent storm dumped debris + rain and diluted your chemistry.

The SLAM method fixes all four causes at once by aggressively over-chlorinating for several days while you brush and filter continuously.

The SLAM method, step by step

You need: a real test kit (Taylor K-2006), enough shock to hit the target FC, a pool brush, and a filter that runs 24/7 for the duration. Plan on 3–7 days.

  1. 01
    Test everything — especially CYA
    Test FC, CC, pH, alkalinity, and CYA. CYA is the number that determines your target shock level. Higher CYA = you need more chlorine to actually sanitize. Rough rule: shock target FC ≈ 40% of your CYA. So CYA 40 → shock to FC 16. CYA 80 → shock to FC 32.
  2. 02
    Balance pH to 7.2–7.4 first
    Chlorine works best at slightly acidic pH. High pH during a SLAM cuts effectiveness in half. If pH is above 7.6, add muriatic acid to bring it down before you shock. Wait an hour, then move on.
  3. 03
    Add shock — cal-hypo or liquid chlorine
    Cal-hypo (calcium hypochlorite, ~65% chlorine by weight) is what most bags at the hardware store are. Liquid chlorine (12.5% sodium hypochlorite) is easier to dose and doesn’t add calcium, but heavier to buy in bulk. Either works. Add with the pump running, spread around the perimeter — don’t dump in one spot.
  4. 04
    Brush every visible surface
    Algae hides in the micro-cracks in plaster and behind the tile line. If you don’t brush, you leave it alive to bloom again as soon as your chlorine drops. Brush the walls, steps, and any dark corners at leasttwice a day during a SLAM.
  5. 05
    Run the filter 24/7
    Yes, all night. The filter is what actually removes the dead algae from the water. If you have a cartridge filter, expect to hose it out every day during a SLAM. Sand/DE filters need daily backwashing. Pump running non-stop is what turns green → cloudy → clear.
  6. 06
    Re-shock every morning + evening
    Test FC 2x per day and re-shock back up to your target every time it drops. This is where SLAMs fail — overnight the FC drops back to sanitizing levels and the algae recovers. You’re holding the target FC 24/7 for the whole duration.
  7. 07
    Watch for the color change
    Day 1–2: bright green → murky green
    Day 2–4: murky green → gray/cloudy
    Day 4–6: cloudy → hazy → clear
    Day 6–7: clear enough to see the main drain.
  8. 08
    Pass the overnight chlorine loss test
    When you think you’re done: test FC in the evening after sunset, then again first thing in the morning before sunrise. If you lose 1 ppm or less overnight, the SLAM is complete. If you lose more, algae is still alive — keep going.

When to stop DIY-ing and call

Some green pools aren’t worth fighting alone. Call a pro (me or somebody else) if:

  • The pool has been green for weeks and there’s black stuff in the corners (that’s black algae — different beast, needs mechanical + chemical treatment).
  • You can’t see the second step down.
  • Your CYA is above 100 (you probably need to drain and refill; a full drain on a filled pool needs care so the shell doesn’t pop out of the ground).
  • You’ve been SLAMming for 10+ days and the color isn’t changing.
  • You have kids/pets and you just want the yard usable this weekend.

A green-to-clear rescue with me runs $150–$500 depending on severity — usually 2 visits over a week.

Chemical only
Chemistry, handled.
You just clean.

Weekly photon-reader testing and all chemicals included — flat $150/mo. You keep doing the physical cleaning.

Doing it yourself
With Chemical Only
Chemicals
$110–$140 / mo at Lowes
Included — tabs, shock, acid, stabilizer, algaecide, whatever your pool needs
Water testing
Strip test (drifts every 6 mo) or monthly supply-store dip
Photon reader — same weekly, on-site
Your time
30–60 min / week
None — you just clean
Monthly total
$110–$140 + your time
$150 flat
Text me about Chemical Only
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