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Hot Tub & Spa Chemical Dosing Instructions - H2oFun

Hot Tubs Spas have increased in popularity, especially over the Covid-19 Lockdown period, with both inflatable and rigid spas selling out in 2020. "Hot Tub" or "Spa" are the same product, just called different names, most often based on where in the world they were manufactured. Both are products to facilitate relaxation or therapy in water that is a hotter temperature than a swimming pool. 

Whether you call yours a Hot Tub or a Spa it is essential that good water quality is maintained, ensuring bather safety and comfort. The chemistry and process is the same in looking after a Hot Tub Spa as a swimming pool, but they do need more attention to keep the levels correct, due to the smaller volume of water with heavier bathe loads. 

It is useful if more than one member of the family is competent in using and understanding the chemicals used, why they are being used and what reaction they should have. 

If you follow H2oFun's Hot Tub Spa Chemical Dosing Guides, along with always reading the labels on each chemical, it should make it easier to keep all your family and friends safe.

Terms You Will Need To Know The Meaning Of


pH is the test to show if your hot tub water is acidic or alkaline (base). The pH scale runs from 0-14, 7 being Neutral, but the desired and ideal level for your spa is between 7.2 to 7.4. Test this with good quality test strips. We recommend Aquachek Test Strips to test, as we have found they have the highest accuracy, then adjust using Fi-Clor pH Increaser or Reducer which is the highest quality chemical brand. 

Chlorine Aquachek Test Strips Click Here 

Bromine Aquachek Test Strips Click Here

Fi Clor Hot Tub pH Reducer Click Here

Fi Clor Hot Tub pH Increaser Click Here



Chlorine or Bromine levels are described in PPM (parts per million). Aim to have your Hot Tub Chlorine or Bromine levels between 2ppm - 3ppm. We recommend using Fi-Clor Chlorine Granules and Chlorine Tablets and Fi Clor Bromine Granules and Bromine Tablets in your Hot Tub

Fi Clor Spa Chlorine Tablets Click Here

Fi Clor Spa Chlorine Granules Click Here

Fi Clor Spa Bromine Tablets Click Here

Fi Clor Spa Bromine Granules Click Here

Chlorine Aquachek Test Strips Click Here 

Bromine Aquachek Test Strips Click Here


Shock Dosing

Shock Dosing is when an oxidiser is added to raise the Chlorine levels to between 5-10ppm or if using Bromine as the sanitiser then add Non-Chlorine Shock. This will help clear cloudy water by destroying organic matter and pathogens in the water and freeing the Chlorine and Bromine left in the water.

Shock Dose the Hot Tub Spa at least every two weeks, or when necessary.

Fi Clor Spa Chlorine Superfast Shock Click Here

Fi Clor Spa Non-Chlorine Shock Click Here 



Buy a good quality test strip and test regularly. It will help you keep your family safe and your hot tub spa water clean and clear

Chlorine Aquachek Test Strips Click Here 

Bromine Aquachek Test Strips Click Here


Water Balancing

Testing and balancing the pH and alkalinity levels in your Hot Tub Spa will let your Chlorine or Bromine work effectively and protect you heater, pumps and pipework from acid or scale damage. Correctly balancing your pH and Alkalinity levels will help ensure crystal clear water and add years of life to your hot tub pumps and heater.

Fi Clor Hot Tub pH & Alkalinity Reducer Click Here

Fi Clor Hot Tub pH Increaser Click Here

Fi Clor Spa Alkalinity Increaser Click Here


Hot Tub Spa Fi Clor Chemical Dosing Guide - Always Read The Label

 Ideal Levels Initial Quantity (per 1000 Litres) Fi Clor Chemical On A Regular Basis (per 1000 Litres)


3ppm (mg/l)


Fill Dispenser

Spa Chlorine Granules

Spa Chlorine Tablets

2gm to raise 1ppm

Check tablet level


5ppm (mg/l)


Fill Dispenser

Spa Bromine Granules

Spa Bromine Tablets

3gm to raise 1ppm

Check tablet level



Spa pH Reducer

Spa pH Increaser

10g reduce 0.2ppm

10g raise 0.2ppm



Spa Alaklinity Increaser

Spa Alkalinity Reducer

30g raise 10-20ppm

20g reduce 0.2ppm

Calcium Hardness

Less Than 250ppm

Spa Hardness Increaser  10g raise 10ppm

Scale Inhibitor

Essential In Hard Water Areas

Spa Anti-Scale 50ml - 100ml


Hot Tub Spa Size / Water Volume Guide 

Length x Width x Average depth in Mitres = Cubic Metres = 1000 Litres

e.g. 2m x 2m x 0.3m = 1.2m/3 = 1200 litres



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