Castle Hot Tubs

5kg Castle Hot Tubs pH Plus



5kg Castle Hot Tubs pH Plus / pH + is a granular balancer used to increase or raise the pH of your hot tub, spa or swimming pool.pH is a measure of how acidic or how basic water is. The pH range goes from 0 to 14, with 7 being neutral. A pH of less than 7 indicates acidity, a pH of greater than 7 indicates a base. The pH of water is a very important measurement concerning the water quality of your hot tub / spa or swimming pool.A high pH level in a pool or hot tub water can cause limescale build up, which can damage working parts including pumps, heaters and seals.

How to raise the pH?
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.

How to 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 Repeat until the ideal pH is established 

You can test your water one of three methods:
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.


If you require delivery to the Scottish Highlands & Islands, Isle of Man, Scilly Isles, Channel Islands, Northern Ireland or outside of the UK mainland please contact us for a postal quote before making your purchase. Thank you.

Product Specification

  • Increases PH of Pool, Hot Tub or Spa Water
  • Helps prevent foaming and reduces the risk of damage to plastic parts.
  • Fast and easy to use granules. Dosage instructions are included
  • For the best/safest bathing experience always keep your PH between 7.2 and 7.6 as shown on your test kit/strips.
  • Top Quality branded product from Castle Hot Tubs

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Rebecca G

Good firm to deal with


Bought the 5kg tub as it was only slightly more expensive than the 2kg tub so better value

Phillip E

PH +


The larger size container is much better valued than what we bought previously

Carol M


John D