Hot Tub Water Care – Chemistry Guide

pic Hot-Tub-Water-Care

Hot Tub Water Care – Chemistry Guide

The environment influences water conditions in a Wood-fired Hot Tub.  There are three types of pollution:

  • Physical pollution. It can include trash brought by the wind (sand, flower pollen, leaves) or things appearing due to bathing (skin particles, hair, cosmetics)
  • Biological pollution. Raw water is often subject to “blooming”, that is, some blue-green algae appear.
  • Chemical pollution. A plenty of rainwater can influence the pH-balance of water in a Wood-fired Hot Tub and make it too acid.

After you fill your Wood-fired Hot Tub with water for the first time, we advise you to perform several simple steps to arrange safe conditions for bathing and economizing water usage.

Step 1. Measure and control pH value.

Permissible рН level varies from 7,0 to 7,4. The value of рН = 7,2 is usually referred to as neutral.

pic test-stripes

If pH level is too high, the water is called hard. Bathing in water with high pH level can result in skin irritation, itching and red eyes. Hard water negatively influences your Wood-fired Hot Tub by causing excess marly sediment on nozzles and other metal elements. When pH level is lower than 7,0, the water is too soft. Not only does it accelerate the corrosion rate of metal elements (pipes, metal surfaces in the filter or burner), but also creates favorable conditions for pathogens fast growing.

Baltresto online-shop offers safe Swim & Fun test stripes that will show You the current pH value easily and quickly.

Step 2. Disinfection.

There are two ways of water disinfection:

1. The usage of chlorine substances.

The most common and proven method of disinfecting water is chlorination. Slow chlorine tablets are placed into a floating chemical dispenser protected from children. Depending on the operating and weather conditions, these chlorine tablets are slowly dissolving in water within 1-2 weeks, preventing the growth of bacteria.

Attention! Always take the dispenser out of a Wood-fired Hot Tub when bathing!

pic chlorine WeekTab-1kg,-20g-tablet

2. The usage of oxygen-activated substances.

Disinfection with KiddyPool active granules is an easy way to avoid the chlorination of water and have it safe for your children. One pouch cleans up to 600 litres of water and keeps it hygienically fresh for 2 weeks.  KiddyPool effectively works against germs and spores in water. It is excellent for both fresh and sea water, does not foam and has a neutral pH value.

pic disinfection-kiddy-pool

Step 3. Choosing of the water filtering system.

When the effective filter has been correctly chosen, you won’t have any cloudy water, thus reducing your expenses on changing water.

The filter works in the following way: it purifies water from various types of natural and physical impurities by passing a great water volume through the filler.

We recommend using two types of fillers that have shown the best performance in terms of price/quality ratio:

pic sand filter for wood-fired Hot Tub

1. Traditional sand filter is a plastic tank filled with sand through which water is pumped with electricity.

Different impurities, if the size of particles does not exceed 20 microns, deposit in the sand. As water passing through sand is gradually polluting it, we recommend cleaning the filtering system regularly. To do this, it is necessary to wash the filler with water several times, until the liquid with sand becomes transparent.

pic Fiber filter balls

2. The filter with pool fiber-balls is the most modern and economical solution for Wood-fired Hot Tubs (700g fiber-ball = 25 kg sand). Pool fiber-balls have the following advantages:Thorough filtration traps particles with the size up to 5 microns.

  • They do not harden and stick together like sand.
  • They are very easy to use due to their little weight (it is not necessary to lift heavy bags with sand up to 25 kg).
  • They are reusable, non-toxic and environmentally friendly.
  • They are easily utilized with standard household rubbish.
  • They are resistant to chemical substances of the pool.

Step 4. The removal of coarse litter

Coarse sediments, for example leaves, grass or hair should be removed from the water surface with a skimmer.

The best solution for a Wood-fired Hot Tub is a suspended skimmer, it is an automatic device that should be mounted onto the internal pool edge. The skimmer pumps the surface water, then it is filtered, warmed up and returned back being cleaned. A drainpipe is attached to the skimmer through which the clean water flows back into the tank. We recommend installing a suspended skimmer onto the windy side: this will allow all small objects which are in the water to get into the device themselves, and cleaning will go faster.

The use of a skimmer reduces the quantity of disinfectants to be used as well as the wastage of a filter pump.

pic skimmer wood-fired Hot Tub

Consider the main problems with water and ways of their solution:




1.Water is green and cloudy Algae appear in the water due to lack of chlorine or pH value is too low Control pH value using the pH+ kit
2. Walls of a wood-fired Hot Tub are slippery Algae appear in the water due to lack of chlorine or pH value is too low Control pH value using the pH+ kit
3. Water is milky and cloudy pH level is too high, water is too hard, there are lime particles in the water. Control pH value using the pH+ kit. Turn on the pump to start the filtering system.
The water has the insufficient quantity of disinfectant. Check the disinfectant quantity in the water and pH level. Perhaps, you will have to replace or increase the dosage of tablets for chlorination.
4. Water is brown but clean. There are brown impurities (particles) in the water. There are particles of iron in the water (yellow-green color) or copper (turquoise color). Control pH value, turn on the filter with the pump and partly change the water.
5. Water is brown and cloudy There are too many particles of iron in the water. Control pH value, turn on the filter with the pump and partly change the water.
6. Water is black and cloudy There are too many particles of magnesium in the water. Control pH value, turn on the filter with the pump and partly change the water.
7. Water is black and cloudy There are too many particles of magnesium in the water. Control pH value, turn on the filter with the pump and partly change the water.
8. There is some sensible coating on walls of a Wood-fired Hot Tub pH value is too high, water is hard which leads to the forming of lime deposits. It is necessary to pour the water out of a wood-fired Hot Tub  and remove the coating with some gentle  bleach.
9. pH and chlorine values are standard but water is still green There is too much stabilizer/cyanuric acid in the water. Check the water for cyanuric acid and partly change the water in a wood-fired Hot Tub.
10. Rusting appears on metal elements pH value is too low, so the water is too soft. Control pH value using the pH+ kit


To avoid problems with water and enjoy using your Wood-fired Hot Tub, Your measurements have to be in the indicted permissible limits:

pH values рН 7,0-7,4 (goal – 7.2)

Free chlorine * 1,0-3,0 mg/l

Fixed chlorine * Max/ 0,5 mg/l

Active oxygen 3,0-8,0 mg/l

Cyanuric acid 25-50 mg/l

Total alkali 80-120 mg/l

Calcium hardness 100-200 mg/l

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