Hot Tub pH Increaser Relax 1Kg pH Plus


Relax pH Plus / pH + granules are a dry granular balancer, used to increase or raise the pH of your hot tub / spa / swimming pool water.


Have you considered our own brand version of this product?

Castle Hot Tubs Range

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Hot Tub pH Increaser from Relax.  pH Plus / pH + is a granular balancer used to increase or raise the pH of your hot tub / spa / swimming pool water.

Fast and easy to use. Dosage instructions included.

Why do I need to use a Hot Tub pH Increaser?

Raise the pH level in your hot tub, spa or swimming pool water.  A low pH level in hot tub, spa or swimming pool water can cause staining or corrosion, which can damage working parts including pumps, heaters and seals. A low pH level may also lead to foaming and damage to plastic parts. To prevent this issue, use pH Plus.

How do I know when pH needs to be raised?

Test the water using pH test strips, if your pH is below 7.2, use pH Plus to bring the pH to between 7.2 and 7.6 on your test kit/strips.

Confused about your hot tub water chemistry? Our guides answer the most Frequently Asked Questions!

Read our how-to guide on balancing your hot tub / spa / swimming pool water pH levels

How do I use pH Plus?


  • Consult label for dosage instructions and handling precautions
  • Pre-dissolve the product using clean warm water
  • Carefully add the resulting solution to the hot tub / spa / pool water
  • Re-check the pH level
  • If necessary repeat the treatment until the ideal pH is established

A genuine Relax branded product.


Relax pH Plus 1 Kg
– Directions for use –
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Why don’t you try our own brand instead

All of Castle Hot Tubs branded products are Grade ‘A’ quality – packed and labelled in the UK