You are here: Pool & Spa Care > FAQs

How much Natural Pool and Natural Spa Clarifier do I need?

For hot tubs, spas and swimspas 5-10mls of Natural Spa Clarifier diluted in a jug (approximately 200mls) of fresh or hot tub water per 1000 litres (220 gallons) of water.

For swimming pools and hydrotherapy pools 25mls of Natural Pool Clarifier diluted in a jug (approximately 200mls) of fresh or pool water per 10,000 litres (2,200 gallons) of water.

If your water is particularly cloudy you can use three times the recommended dose. Contact us if you need specific advice for your pool or hot tub.

Back to top

Do I need to use a sanitiser?

Yes! Good sanitation is essential for a healthy pool or hot tub. Sanitisers make the contaminants in the water safe, but they don’t remove them. Pennosan multi-functional Natural Pool Clarifier and Natural Spa Clarifier remove contaminants that typically use up sanitisers, making the sanitisers more efficient.

Back to top

What order should I put the chemicals in?

Whether you have a swimming pool, hot tub or swimspa, it’s important that your chemicals are well balanced and (ideally) added in the correct order. Don’t stress too much if you get it wrong on occasion, but do try to use the following order as a guide.

  1. TA – acts as a buffer for the pH. If too high or too low, you’ll struggle to balance the pH. Ideal range is 80-120ppm (parts per million).
  2. pH – the higher the pH, the harder it will be for the chlorine to do its job of sanitising your water. It’s really important that the pH is within the recommended range of pH7.2 – pH7.4, for this reason (try to keep it closer to pH 7.2 if you can).
  3. Sanitiser – only when the first two are within the right range, should you address the sanitiser.
    3.1 – a shock dose is necessary on a fresh fill. Ideally, you should use chlorine shock for this. (You can use stabilised chlorine granules, but it will take longer for the chlorine to reduce and you’re adding stabiliser unnecessarily). Add enough chlorine (follow the guidelines on the container) to maintain free chlorine at 10ppm for at least 5 hours. Then wait for the chlorine level to drop to 3-5ppm (usually overnight).
    3.2 – after the shock dose of chlorine has decreased, maintain sanitiser level at 3-5ppm FREE chlorine or 4-6ppm FREE bromine, depending on which sanitiser you use.
  4. Pennosan Natural Spa Clarifier, diluted in fresh or hot tub water, is best added when TA, pH and chlorine are in the desired range. The recommended dose for maintenance is 5-10mls per 1000 litres. If your hot tub is particularly cloudy, there are lots of people using it or you want to safely wear sunscreen in the tub, you can safely increase the dose amount and frequency.

Back to top

What is total alkalinity (TA) and why is it important?

TA (Total Alkalinity) is measured in parts per million (ppm) and affects how much the pH of the water changes when other chemicals are added. Maintaining TA in the region of 80-120ppm prevents pH fluctuation when chemicals are added to the pool or hot tub. TA will reduce naturally over time, so it’s important to check and correct first. If you are in a hard water area, the TA in the water coming out of your tap could be naturally higher than 250ppm. Here you will need to use a TA reducer or a pre-filter which attaches to your hose and filters the water before it enters your tub.
The recommended range for TA is 80-120ppm (parts per million or grams per litre).

  1. If TA is too low (below 60ppm) there can be rapid changes in pH, corrosion of exposed metal parts, eye irritation and in some cases a coloured tint (usually green) to the water.
  2. If TA is too high (above 160ppm), it can lead to the pH being resistant to change and difficult to adjust (“pH lock”). It can also cause cloudy water.
    To increase TA by 10ppm in 1000 L add 18 g of TA increaser or bicarbonate of soda.
  3. Always follow instructions on the container.

Back to top

What is pH and why is it important?

The degree of acidity of the water is measured by its pH value on a logarithmic scale of 0-14, with 7 being neutral. Pure water has a pH of 7. As the pH number falls below 7, it becomes more acidic and increasingly corrosive to pool and hot tub parts as well as causing skin and eye irritation. As the pH number rises above 7, it becomes more alkali, chlorine becomes progressively less effective and the water may become cloudy with scale forming.

Free chlorine is made up of two components:

  • Hypochlorous acid (a very effective sanitiser).
  • Hypochlorite ion (a very weak sanitiser).
  • The relative proportions of these two compounds is strongly related to pH.
  • At pH 7, about 80% of the free chlorine is in the form of hypochlorous acid.
  • At pH 8, about 30% of the free chlorine is in the form of hypochlorous acid.



Swimming pool and hot tub water should be maintained within the ideal range of pH 7.2 to pH 7.4.

Back to top

What is total chlorine and why is it important?

Total chlorine is the measurement of the Free Available Chlorine and Combined Chlorine present within the pool or hot tub. Free available chlorine should always be at least twice the level of combined chlorine and combined chlorine should always be maintained at below 1ppm – this is known as “breakpoint chlorination”. To calculate the amount of combined chlorine, simply subtract free chlorine from total chlorine.

Back to top

What are chloramines?

As free chlorine is added to the pool or hot tub, it reacts with pollution to form chloramines.

Chloramines (sometimes referred to as disinfectant by-products – DBPs) are formed when chlorine reacts with ammonia from sweat, oils and urine introduced to the water by bathers.

Chloramines are a much less effective sanitiser when compared to chlorine and, if incorrectly managed can be more irritating to the skin and mucous membranes, as well as producing that classic “chlorine” smell often associated with swimming pools. Think of chloramines as being ‘used up’ chlorine. You will need to use either a chlorine or non-chlorine shock treatment to oxidise the chloramines and free up the chlorine to do its job of sanitising your water.

Even though your water might look crystal clear, and your dip tests say your levels are correct, unless you are also measuring the TOTAL chlorine and the CYA (stabiliser) as well as the FREE chlorine, TA and pH, you can’t know how safe your water is.

You can take action to reduce the amount of chloramines that are formed by using multi-purpose Natural Spa Clarifier or Natural Pool Clarifier.

Back to top

Why do I need to shock my pool or hot tub?

Whenever you fill your pool or hot tub with fresh water, it’s important to give it a shock dose of sanitiser at the start. Some chemical starter kits use stabilised chlorine granules to shock the hot tub, but it is much better to use a proper chlorine shock treatment.

Types of shock treatment:

Chlorine shock is non-stabilised chlorine and is used on a fresh fill to sanitise the tub by removing any bacteria that may be lurking within the system. Chlorine shock can also be used to boost sanitiser levels after a particularly heavy use. Some suppliers provide shock dosages on the packaging of stabilised chlorine granules. We do not recommend to use stabilised chlorine granules as a shock treatment because of the effects of CYA (stabiliser) on the chlorine.

Non-chlorine shock is a powerful oxidiser used to eliminate contaminants in the water. The chlorine or bromine makes bacteria safe but it doesn’t remove the contaminants. A non-chlorine shock will remove chloramines (used up chlorine) and will reactivate bromine, thus maintaining safe bactericidal levels.

Back to top

What is cyanuric acid (CYA)?

Cyanuric acid (CYA) is a weak acid used predominantly in outdoor swimming pools to stabilise the chlorine, protecting the chlorine from sunlight which would quickly break it down. More and more frequently it is used in spas and hot tubs in the form of “stabilised chlorine” (dichlor or trichlor) – i.e., the CYA is already attached to the chlorine. Whenever you add stabilised chlorine granules or tablets to your pool or hot tub, you are adding a proportion of cyanuric acid. Unlike chlorine, CYA builds up in the water over time. This makes the chlorine less effective as a sanitiser, increasing the contact time needed to neutralise bacteria. Because there are higher levels of contaminants present in hot tubs and spas, this increased contact time becomes an issue as the chlorine is struggling to do its job. When CYA reaches 100-150ppm, it’s time to think about a partial dilution (of a swimming pool) or changing the water in a hot tub. The aim should be to keep CYA levels as low as possible (around 30ppm) and to minimise the amount of CYA entering the first place.

Back to top

What is Total Hardness?

Total Hardness (TH) is the measurement of calcium hardness and is made up of dissolved calcium salts and smaller quantities of other mineral salts such as magnesium. TH should be maintained at between 80-200ppm. However, in hard water areas this could easily be exceeded, and a pre-filter may be beneficial.

TH levels less than 80ppm can result in corrosion and higher TH levels can result in increased scale formation. If TH is very low (below 50ppm) it can cause itching and skin irritation.

Back to top

Will this product remove scum lines or tide marks?

Scum lines, or tide marks, are caused by oils & sweat from bathers sticking to the sides of the hot tub. One of the ways that our Natural Spa Clarifier works is by trapping the oils & sweat, preventing them sticking to the sides. With continued use, tide marks will be reduced and eventually eliminated.

Link to Trustpilot review

Back to top

What happens if I get into my hot tub without adding chemicals?

A popular misconception is that you don’t have to treat or balance your bath water so you don’t need to in your hot tub…

It is not advisable to get into a hot tub before properly sanitising the water. Having a soak in hot tub is VERY different to having a soak in the bath.

  • Bath water comes directly from the tap, which is a closed system so unlikely to have any bacteria within it.
  • Bath water is always emptied out after one bathing session.
  • Unless the bath surface is cleaned after use, a scum line from dead skin and oils will form around the sides of the bath.
  • In a hot tub, those oils and dead skin cells that shed into your hot tub water will not only form a scum line, they are nutrients that allow bacteria to grow.
  • The hose used to fill the hot tub may be harbouring bacteria which will then be transferred to the hot tub.
  • The temperature in a hot tub creates a perfect breeding ground for bacteria and they will soon be out of control and at unsafe levels without adequate sanitation.

Taking a little time to balance your hot tub water correctly before first use will save a lot of time and effort in the long run. Correctly balanced hot tub water will generally only require maintenance with Pennosan Natural Spa Clarifier and sanitiser with the occasional shock to maintain crystal clear and safe water.

Back to top

How does this product work with wood fired hot tubs that don’t have filters?

Adding Pennosan Natural Spa Clarifier to a clean tub before use will prevent tide marks, or scum lines, forming in your hot tub. If the water looks a bit cloudy when you come to empty it, add another dose, mix with a paddle (or your hand) and leave for half an hour before emptying. This will make cleaning much easier and less time-consuming.

Back to top

What makes our products different from other clarifiers?

Unlike a chemical clarifier, Pennosan Natural Pool and Spa Clarifiers are naturally attracted to dirt and oils, as well as dissolved metals and micro-organisms. Each product has been formulated by carefully selecting the best ingredients for the required use. We are constantly developing new formulations and often work with our customers to find the best solution for their situation. All our products are made with natural, sustainable ingredients.

Back to top

What is the difference between Pennosan Natural Pool Clarifier and Natural Spa Clarifier?

All of our products have been carefully formulated to address the conditions in which they will be used. Swimming pool and hot tub conditions differ mainly by volume, temperature and bather load which is why we have specific products for each application.

Back to top

If I use this product, can I wear sunscreen and still use my hot tub?

Yes! Unlike most chemical clarifier products on the market, our Natural Spa Clarifier captures oil, grease and pigments from sunscreen and other cosmetics for easy removal via the filtration system.

Back to top

What are the white bits that have appeared after using this product?

This is good a good sign. The Pennosan Natural Spa Clarifier is doing its job nicely. It makes the invisible (dissolves solids that consume the sanitiser) become visible so that it can be easily removed via the filtration system. Depending on the efficiency of the filtration system, this should clear within a few hours, up to a day or two.

Back to top

What is Chitosan?

Chitosan is a natural fibre prepared from crustacean (crab) shells that would otherwise go to waste. Chitosan fibres biodegrade in the environment after use. 

Back to top