- By Andrew Astonville
- Published 06/1/2012
It’s important to be aware that hot tubs and spas are set at a temperature that is very friendly to bacteria and other contaminants, so it’s essential to sanitise and care for them on a regular basis.
If you don’t use the correct amount of chemicals, you could damage not only the hot tub’s structure, but also your skin and eyes. Another issue is that while hot tub retailers sell chemical kits that specifically tackle sanitisation, they may or may not be effective depending on the type of water you have.
The following guide will give you some key advice to help you keep your hot tub or spa’s water at the right level of balance for both safety and appearance.
Testing Your Fill Water
Testing the water you fill your hot tub with determines its Ph and total alkalinity (TA), which in turn affects how well a particular sanitizer (such as chlorine or bromine) will perform. You can do this using simple test strips bought at any pool care outlet.
Scale forming water will have a high Ph and TA, corrosive water will have a low Ph and TA, and well water might have problems such as high iron content or tannins. Most city water that we receive in our homes however is generally treated to the correct levels for Ph and total alkalinity – the ideal range is Ph is 7.2 to 7.8, with a TA of 80 to 140.
Remember that if your Ph and alkalinity are high, scale can form on your heater element and on the hot tub shell itself. While this can easily removed with muriatic acid, the scale on your heater element will remain and cause problems with heating the water. On the other hand, if your Ph and alkalinity are low, the acidity of the water will eat into anything metal or plaster, not to mention the heater element which will result in cause water coming into contact with the electrics and thus cause them to short out.
Correcting Ph and Total Alkalinity
High Ph and TA
If your water’s Ph and TA are measuring at very high levels (Ph 8+ and TA 140+), you’ll need to add an acidic chemical to lower them. White vinegar or the Ph Down from your cleaning kit will do the trick – the way to go about this is slowly, since if you over correct you could end up with the even worse problem of corrosiveness.
You will need to run your hot tub for at least 6 hours after chemical corrections have been made. Thereafter use your test strips to fully determine whether the new levels are as they should be.
Low Ph and TA
One of the best chemicals to use for this scenario is Sodium Bicarbonate – good old Baking Soda will be just the ticket to lower your hot tub’s Ph and TA, however do not use related chemicals such as Soda Ash or Sodium Carbonate as they are much too harsh for this purpose. Simple Bicarb will feed the total alkalinity of the water, which in turn will slowly raise the Ph.
Iron and Tannin Problems
If you don’t live in the city, your fill water might contain incorrect levels of iron and tannins that could negatively affect your skin, the structure of the hot tub and the clarity of the water itself.
When it comes to metals, there are two main types of products to rectify this issue. The first kind sequesters the metals so they can be filtered out, although you will need to be careful of your filter becoming clogged in this case. The other type surrounds the metal to keep it from sticking to the walls or other surface of the hot tub or spa. Do ask your supplier for advice on which type will suit your particular needs best.
Regarding tannins, these are organic materials so they can be removed using a specialised bleaching agent. Again, make sure to get thorough advice on this from your hot tub supplier.
If the water in your hot tub or spa starts to look murky, it’s best to give it a shock treatment of chemicals, since cloudy water often spells bacteria and other harmful contaminants. While products such as Dichlor in a heavy dose can correct such bacterial problems, be aware however that they are not sanitising agents such as chlorine or bromide which need to be administered frequently.
Potassium Monopersulfate is a good shock treatment to use – it works to reduce the chlorines which have combined with bacteria, so the newly freed chlorine molecules are once again effective disinfectants.
Hot tubs also need to be drained periodically, so if it’s been awhile since you last did this, the cloudy water could simply mean that a fresh fill is your best option.
The above guide gives you some useful advice on maintaining hot tubs or spas correctly by keeping an eye on the water’s Ph and TA levels, as well as other elements which will damage the water’s balance such as iron and tannins. Part 2 of this guide series will provide helpful tips on water sanitisation.
About the Author: Andrew Astonville is an independent advisor on hot tubs.