Water Scale Inhibitor

Block calcium scale on heaters, jets and waterlines before it forms. A weekly low-dose phosphonate that holds calcium in solution even in hard-water areas.

• Holds calcium and magnesium in solution to prevent scale.
• Protects heater elements, jet faces and waterline tiles.
• Restores flow on slightly scaled equipment over time.
• Compatible with chlorine, bromine, MPS and salt systems.
• Designed for hard-water areas with TH above 250 ppm.

Sizes and prices

• 1L: £9.78
• 2.5L: £16.35
• 5L: £27.29
• 10L: £49.18
• 20L: £92.95
• 25L: £114.84

When you need it

• You live in a hard-water area (TH > 250 ppm at the tap).
• Calcium hardness in the tub is approaching 250 ppm.
• White scale is starting on heater elements or jet faces.
• Water temperature is held above 38 C for long periods.
• You want to extend the life of an aging heater.

How to use

1. Test calcium hardness, pH and total alkalinity.
2. Switch the circulation pump on and remove the dispenser.
3. Pour 10 ml of Water Scale Inhibitor per 1000 L weekly into the skimmer.
4. Run circulation for at least 30 minutes.
5. Retest pH 24 hours later; rebalance if drift exceeds 0.2 units.
6. Repeat dose weekly while hard water is present.

Dosing guide

Weekly maintenance dose. Double the dose for the first week if scale is already present, then return to the standard rate.

• For 1,000 L, add 10 ml to reach Maintenance.
• For 1,500 L, add 15 ml to reach Maintenance.
• For 2,000 L, add 20 ml to reach Maintenance.
• For 5,000 L (swim spa), add 50 ml to reach Maintenance.
• For 1,500 L, add 30 ml to reach Initial week (scale).

How it works

A blend of organophosphonate and polymer scale inhibitors selected for hot tub and spa duty across pH 7.0-7.8 and water temperatures up to 40 C.

Phosphonates bind to the first calcium and magnesium ions that approach a heated surface, blocking the seed crystals on which larger scale would otherwise grow. The polymer fraction keeps any micro-scale particles dispersed so they remain in suspension and rinse out at the next water change.

Above 38 C calcium starts coming out of solution far faster than at room temperature. A scaled heater loses up to 30% of its output and a scaled jet face restricts flow. Weekly dosing keeps surfaces clean and protects equipment.

Frequently asked questions

How often should I dose?

Once per week as preventative maintenance in hard-water areas.

What is hard water?

Water with total hardness above 200 ppm. Most of southern and central England is in this band.

Will it remove existing scale?

It will slowly dissolve light scale over weeks. Heavy scale needs descaling at the next water change.

How long does 1 L last?

Around 6 months of weekly dosing for a 1500 L hot tub.

Is it safe for salt-water systems?

Yes. It protects salt chlorinator cells, which are particularly prone to scaling.

Do I still need to balance calcium?

Yes. The inhibitor prevents scale formation but does not replace calcium balancing.

What is the active chemistry?

A blend of organophosphonate (HEDP family) and a low-MW polymer for crystal modification.

Does it raise phosphates?

Slightly. 10 ml per 1000 L adds about 1-2 ppm phosphate, well below algae-feeding thresholds for hot tubs.

Will it interfere with sanitiser?

No. The phosphonate is inert to chlorine, bromine and MPS at recommended doses.

Scale still forming?

Calcium hardness is above 400 ppm or pH above 7.8; refresh water and rebalance.

Cloudy water after dosing?

Existing scale dissolving; run filter 24 hours and clean cartridge.

pH drift after dosing?

Mild alkali shift; dose pH minus to return to 7.4.

Scale inhibitor vs descaler?

Inhibitor prevents new scale and slowly removes light deposits. Descaler is a strong acid product used during a water change to remove heavy scale.

Scale inhibitor vs lowering calcium?

Lowering calcium below 150 ppm causes corrosion. The inhibitor lets you hold safe 200-250 ppm hardness while still preventing scale.