Water Chemistry /
What Chemicals Do I Need to Open My Pool?
Most pool openings start with a test kit, then only the chemicals your water actually needs: sanitizer, pH adjuster, and sometimes algaecide or shock.
Archive date: this article was written for PoolSkimmer on Oct 24, 2026 and given the earlier archive date of Jan 11, 2026 so the blog reads as an organized archive. It was not published on that date.
Opening your pool: the chemicals you will need
The process for most homeowners is straightforward. You begin by testing the water and then put in only those pool chemical products that your results indicate are necessary. As a rule, this involves a sanitizer and something to bring the pH into balance. If the pool is opening up on the cloudy or green side, you may also require shock or an algaecide. The precise combination is a matter of what the product label and the condition of your pool and filtration system dictate.
What is typically required?
You can expect to use some of the following when you open the pool:
- A chlorine-based sanitizer for disinfection
- An agent to raise or lower the pH if it is not within the proper range
- Shock to clear up any odour or dullness left over from winter
- Algaecide where there is visible growth
- A stabilizer or alkalinity adjuster, but only if your tests show those numbers are off
Hayward’s approach to pool opening is to treat chemicals as a necessity rather than a set shopping list. By adhering to the manufacturer’s directions for each one, you are taking the safest course to keep your water chemistry in check without over-treating it.
Preparing to add chemicals
To avoid wasting product on unclean water, follow a logical sequence:
1. Clear the surface of any large debris. 2. Shut down the pump prior to getting at the skimmer basket. 3. Make sure the skimmer basket is clean and flow is unobstructed. 4. Give the walls, steps and fixtures a good brushing to dislodge grime. 5. Put the circulation on and run a test. 6. Apply the chemicals the test has called for.
According to Hayward, the extra effort of vacuuming and cleaning the skimmer will make both the filter and the chemistry more effective.
Is shock a must?
Not necessarily. While it is standard practice if the water is contaminated, cloudy or just looks dull, there is no blanket rule for every above-ground or in-ground pool.
There are some important caveats to observe:
- Never mix chemicals unless the label instructs you to.
- Do not put in water until it is balanced, clear and disinfected.
- Refrain from guessing at quantities.
- Stay out of the pool and away from any operating suction equipment or outlets.
Deciding what to purchase
Test strips or a kit will give you the answer. Look at the figures for your sanitizer, pH, alkalinity and, if you are running a chlorine system, the chlorine level. Also take note of any cloudiness or algae. Should the test be inconclusive, try again with a new strip and put it against your owner’s manual; target ranges vary from one pool system to another.
Time to call in a pro?
If the water remains green despite your best efforts, or you have reason to think there is a problem with the pump or filter, a qualified professional should be contacted. The same applies if you are at a loss as to which products are compatible with your setup, or if you spot damaged equipment and electrical faults. It is better to have an expert diagnose the issue than to throw chemicals at it and risk your pool or its hardware.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)