pH Decreaser Sodium Bisulphate 4kg | Pool & Spa pH Down
pH creeping too high? pH Decreaser (Sodium Bisulphate) is the fast, reliable way to bring pH back into the ideal range in swimming pools and spa pools, protecting your swimmers from irritation, keeping your chlorine effective, and preventing scale buildup on equipment.
When pH rises above 7.6, chlorine loses up to 90% of its effectiveness, water turns cloudy, and scale builds on surfaces and fittings. A quick dose of Sodium Bisulphate brings it right back into range.
Product Specifications
| Active Ingredient | Sodium Bisulphate |
| Size | 4kg |
| Target pH (Pools) | 7.2 - 7.6 |
| Target pH (Spas) | 7.2 - 7.8 |
| Pool Dosage | 500g per 50,000L lowers pH by approx. 0.5 |
| Spa Dosage | 10g per 1,000L lowers pH by approx. 0.5 |
| Suitable For | All pool and spa types including saltwater |
| Packaging | Resealable moisture-resistant pail |
Key Features
- Sodium Bisulphate Formula. Fast-acting granular pH reducer, the industry standard for lowering pool and spa pH.
- Fast-Acting. Lowers pH within hours of application.
- Dual-Purpose. Suitable for swimming pools and spa pools of all types.
- Prevents Scale Buildup. Stops calcium deposits forming on pool surfaces, fittings, and equipment.
- Boosts Chlorine Efficiency. Chlorine works best at correct pH levels, maximising sanitiser value.
Dosing Guide
Swimming Pools:
- Add 500g per 50,000L to lower pH by approximately 0.5
- Pre-dissolve in a bucket of water before adding to the pool
- Pour near the skimmer or return jet with pump running
- Allow 6 hours of circulation, then retest before adding more
- Never add more than 500g per 50,000L in a single dose
Spa Pools:
- Add 10g per 1,000L to lower pH by approximately 0.5
- Pre-dissolve in a small bucket of water before adding
- Run jets while dosing for even distribution
- Retest after 30 minutes before re-dosing
Tip: Always test pH before and after dosing. Dose gradually, it is easier to add more than to correct an overshoot. Do not add pH Decreaser and chlorine at the same time, adjust pH first, wait 6 hours, then add chlorine. Sodium Bisulphate is corrosive, wear gloves when handling.
Available Sizes
- 1kg Pail - ideal for spas or small top-up doses
- 4kg Pail (this product) - most popular for regular pool maintenance
- 10kg Pail - best value for large pools or frequent use
Recommended Accessories
- 5-in-1 Test Strips - always test pH before and after dosing.
- Alkalinity Increaser 4kg - stabilise Total Alkalinity first to make pH easier to control.
- pH Increaser (Soda Ash) 4kg - use when pH drops too low and needs raising back to 7.2-7.6.
- Crystalline Chlorine 4kg - sanitise at the correct pH for maximum effectiveness.
Frequently Asked Questions
Q: How quickly does pH Decreaser work?
A: pH begins dropping within 30-60 minutes of application. Allow 6 hours of full circulation before retesting and re-dosing if needed.
Q: Can I add pH Decreaser and chlorine at the same time?
A: No, always adjust pH first, wait 6 hours, then add chlorine. Adding both together reduces the effectiveness of both chemicals.
Q: What if I add too much and pH drops too low?
A: Use pH Increaser (Soda Ash) to bring it back up. Always dose gradually and retest before adding more to avoid overcorrecting.
Q: How often will I need to adjust pH?
A: Test weekly during summer and after heavy rain or high bather load. Spas should be tested after every use.
Q: Is Sodium Bisulphate safe for all pool types?
A: Yes, safe for concrete, fibreglass, vinyl liner, and tiled pools, and all spa pool types when used as directed.
Q: Why is my pH always rising?
A: Common causes include saltwater chlorinators, high Total Alkalinity, and aeration from jets or waterfalls. Check your Total Alkalinity first, if it is above 120 ppm, lowering it will help stabilise pH naturally.
Pickup and Delivery
Perfect Pools Service Warehouse - 15C Douglas Alexander Parade, Albany, Auckland
Hours: Mon-Fri 9am-4pm | Sat 10am-2pm
NZ-wide delivery available. Charges calculated at checkout.
Questions? Email perfectpoolsnz@gmail.com or visit our contact page.
