This is a question I am asked more and more these days.  

I can certainly understand why, given the growing popularity for taking a relaxing dip in a tub!  

By 2015, according to the British and Irish Spa and Hot Tub Association, around 100,000 hot tubs had been installed in the UK, making us one of the world’s top ten hot tub markets.  More recently, with so many people being forced to stay at home during lockdown, hot tub sales have gone through the roof.   

The South of England (prime Scott Jenkins Water Softeners territory!) certainly has its fair share of hot tubbers. But it’s a region that also has some of the hardest water in the country, which is why more and more people are turning to softened water. It’s easy to see why, since soft water has so many advantages over hard water, a subject we cover extensively in other articles within our Knowledge Centre. 

But what’s the verdict when it comes to hot tubs? Is soft water better to use than hard water, or vice versa. 

The answer is – you CAN use both. Softened water is safe to fill your tub with and so is hard water. However, this answer comes with provisos.  

Why can hard water or soft water be bad for my hot tub?

Excessively hard water, resulting from the amount of calcium and magnesium minerals it contains, can be a real nuisance in a hot tub – as with elsewhere around the home. 

In the south of England, especially around Sussex, Surrey and Hampshire, the mains water supply is generally considered to be hard to very hard – anything from 180-340 parts per million (ppm) of minerals content. That’s too hard for use in a hot tub. If left untreated, in a relatively short period of time, it can create harmful scaling, corrosion and clogging up of pipework. It will also leave unpleasant limescale deposits on your hot tub. Not nice to dip in to!  

On the other hand, water that has been softened is probably not suitable for your hot tub, without a bit of tweaking, because it can actually be corrosive to metal.    

How do I get the right balance of soft water and hard water in my hot tub? 

To ensure you have a well-maintained, hygienic hot tub, it’s important to strike the right balance between the hard and soft water you empty into it. This comes down to regular testing and treatment of the water. 

To do this, you should regularly test for pH, alkalinity and calcium hardness and make sure that they are maintained within a recommended healthy range. Keeping a steady pH is the key.

What is alkalinity?

Alkalinity is any reading of greater than pH 7.0 and is the overall measurement of all carbonates present in water, including calcium. 

Typically, fibreglass hot tubs are best balanced at a pH of between 7.2 and 7.8. Once that level is stable, it is then preferable to keep these pH levels steady for the best, long term results.       

Assuming your hot tub is getting regular use and isn’t standing empty for long periods, it is recommended that the hardness and alkalinity levels should be tested weekly.

Furthermore, it is worth pointing out that, although optimum levels of soft/hard water will vary between specific products, we would suggest you check with your hot tub manufacturer or supplier as to what they would recommend. 

The case for soft or hot hard water in hot tubs

In summary, you needn’t be concerned about filling your hot tub with either soft or hard water. But just remember to take the necessary precautions. Whether you already have a water softener in your home or you are totally reliant on the mains hard water, if you own a hot tub, you should regularly monitor its pH level. Hard or soft water for your hot tub – what’s it to be? This isn’t one of those situations where there is a cut and dried answer. 

I’m Scott Jenkins and the company I founded, SJ Water Softeners, is now the No.1 local supplier of water softeners for West Sussex, Hampshire, Surrey with a now increasing reach throughout the wider south of England. For further information about our great range of soft water systems, call 01243 607494 or via email: