Why Does My Hot Tub Smell?

It’s not pleasant but smelly hot tubs are all too common. Hot tubs can commonly smell like rotten eggs, fish, chemicals, mint, plastic or just downright moldy. So, why does your hot tub smell so bad and what can you do to fix the problem? If you want to get your hot tub smelling sweet and fresh again read on!

So, why does my hot tub smell? If your hot tub’s water chemistry is out it can make it smell bad. Make sure your PH levels are correct, shock the hot tub and check sanitizer levels. Internal plumbing can also harbor smelly bacteria so try a full flush. Old hot tub covers can collect moisture, mildew and mold and become smelly and filters can also become clogged and harbor bacteria.

Let’s start off by having a look at some common but universally weird and disgusting hot tub smells!

Why does my hot tub smell of fish?

Not nice! A sharp, fishy pungent smell is often due to the PH levels of the water being too low. If the levels are too high it can smell musty and a bit like wet dog!

The solution is simply to keep on top of your PH levels, regularly check them and adjust on a daily basis if needed. Testing is done with a simple test strip and takes moments and you will then simply need to add adjustment chemicals according to the reading.

Why does my hot tub smell of rotten eggs?

The disgusting rotten egg smell is caused by high levels of sulpher bacteria in the hot tub water which react to form Hydrogen Sulphide gas which is the awful smell. It’s not harmful in itself, just extremely unpleasant but an excess of sulphur in the hot tub can damage some metal parts over time if it isn’t addressed.

To get rid of the smell start by cleaning the hot tub filters. Then, shock dose the hot tub and allow the water to go through the filtration system for a few hours. Assuming that the filter is clean and working efficiently it should catch the sulphur bacteria. So, take the filters out again and give them another thorough clean before replacing.

The Hydrogen Sulphide is formed around warm water so the hot tub’s heater could well be contaminated. It is possible to add a solution to the hot tub that is specifically designed to clean the heater so using one of these might be a good idea as well. Hydrogen Sulphide also forms more quickly in warm stagnant water so, if the heater is on and the hot tub is at working temperature but is not being used for long periods of time it is a good idea to periodically set the jets to come on, remove the hot tub cover and aeriate the water.

Why does my hot tub smell of chemicals?

If you are getting a very strong smell of Chlorine or Bromine from your hot tub it means that the chemicals are working extremely hard to keep the water clean. The chances are that your water, even if it doesn’t look it, is dirty or contaminated in some way.

The first thing to do is to shock does the hot tub and to make sure that your PH levels and sanitizer levels are all correct. This might just fix the problem once things have settled down a little bit.

If you still have a problem check the amount of Total Dissolved Solids (TDS) in the hot tub water (easily done with a test strip). If your TDS level is above 1500ppm then it means that the water is saturated with microscopic dirt, debris and organic matter and the water should be changed.

Why does my hot tub smell of mint?

A smell of mint coming from your hot tub could mean that there is bacteria growing in it. Shock the hot tub, check your PH levels, sanitizer levels and also make sure that the filters are clean. If the smell doesn’t go away then drain the water, thoroughly clean the hot tub and start again with fresh water.

Why Does My Hot Tub Smell of Plastic?

A plastic sort of smell coming from your hot tub may well mean that the internal plumbing is covered in biofilm. Basically, this is a covering of smelly gunk and bacteria!

The only way to get rid of biofilm is to thoroughly flush the system through. To do this add a specialist flushing solution to the hot tub water according to the instructions on the packet. Switch on the jets and allow plenty of time for the flushing solution to work and to flush out all of the gunk from the pipework.

The dirt and debris will end up floating around in the water so you now need to do a full drain of the hot tub, thoroughly clean the hot tub shell, refill and balance the water and chemicals.

Why does my hot tub cover smell?

Hot tub covers have to withstand a constant barrage of heat, steam and chemical vapor as well as fend off the external elements. So, it’s no surprise that eventually damage occurs or they just start to get a bit worn out. If a hot tub cover is smelling the chances are that is has mildew or some mold gathering in it somewhere.

In the first instance have a good look around the cover and you may well be able to see the mold forming on the underside or in folds and crevices. The conditions are ideal here for bacteria to grow as it is warm and moist so once started it doesn’t take long for mildew to spread and start smelling.

You also need to check for damage to the hot tub cover and assess whether or not the cover is taking on water. Over time the steam from the hot tub will find it’s way inside the foam core of the hot tub cover and it will then condense into water – a bit like a giant sponge. Obviously, if you have a large body of stagnant water being constantly heated from below it won’t be long until bacteria starts to grow and again this can cause all sorts of problems and smells.

I completely dry hot tub cover should be easily moved by one person but, once it has started to take on water it will get heavier and heavier. So, if yours is starting to get rather weighty and smelly it may well be full of stagnant water.

There are a number of things you can do to dry out a waterlogged hot tub cover but basically the best solution is to take the cover apart and to dry everything out in the sun. If the cover is damaged you will have to have it repaired or you will soon get the same problem again though, and, if your foam cores are completely beyond it then you can buy replacements.

The best thing to do is to try to prevent your hot tub cover from becoming moldy and waterlogged in the first place. The only way to really do this is to remove the cover on a weekly basis and to put it out in the sun to thoroughly dry off. Clean any dirt or mold growth off and inspect the cover for damage and repair before things start to get out of hand.

How can I make my hot tub smell better?

Smelly hot tub water is nearly always due to either the PH levels of the water being incorrect, the internal pipework being covered in biofilm, a waterlogged and dirty hot tub cover or simply dirty and unsanitized water. All of these things can be avoided if you follow a regular schedule of hot tub maintenance and, once you get into the habit of doing it, a bit of regular care will be far less time consuming than trying to fix the smell problem once it has taken hold!

However, if you already have a hot tub smell problem that isn’t really going to help. So what should you do?

Check your water chemistry – Water chemistry is the bedrock of hot tub cleanliness so always start by checking your total alkalinity and PH levels. This is quick and easy to do and you should be doing it on a daily basis anyway. Once you have checked the levels take the time to add balancing chemicals until you have got everything just right. This might take some time – sometimes it takes a while for everything to settle down and it might be that you have to work on this over a 24 hour period if you need to make a large adjustment.

Once you have everything balanced make a mental note to recheck on a daily basis. Your PH levels will change according to the amount of use the hot tub gets and will naturally fluctuate. It can be a really good idea to keep a record in a notebook or on your phone of your daily PH readings and balancing chemicals added. Over time you will come to notice patterns and it will gradually become significantly easier and quicker to keep everything where it should be.

Shock dose the hot tub – The next thing to do is to give the hot tub a mega blast of Chlorine. This shock dosing will kill any bacteria stone dead and should go a long way to solving the smell problem.

Read the packet of the shock granules carefully and make sure that you are adding the correct amount for the capacity of your hot tub. Once the shock is added to the tub leave the jets on to disperse the treatment and leave the cover off the hot tub for a while to allow the chemical vapor to disperse.

The Chlorine levels once you shock dose should be very high, around 8 – 10 ppm. It needs to be at this level to be powerful enough to completely zap the bacteria in the tub. You may need to re – dose the tub or add a second dose to get the chlorine up to this level if your water is contaminated badly.

It’s vital that you don’t get in the hot tub whilst the Chlorine is at this high level. It will, over time disperse and it’s not until it’s between 2-3ppm that it’s OK to get into the water. This might take a couple of hours or it could need leaving overnight.

It’s a good idea to get into the habit of shocking the hot tub after each day of use and then leaving the Chlorine to disperse overnight so that the levels are safe and the water is clean the next day. This regular habit will go a long way to preventing bacteria build-up and smells developing.

Hot Tub Cleanliness – The other thing that will significantly help to keep smells at bay is to keep the hot tub itself scrupulously clean. Get into the habit of using a skimmer to remove any floating debris and also use a pool vacuum to clean up any debris from the hot tub floor.

There’s also no substitute for a bit of good old elbow grease on a regular basis to remove and scum, stains or watermarks from the hot tub shell as soon as they appear and before they start to develop and spread. A hot tub cleaning solution is best for this job.

You will also find that your water stays cleaner for longer if you shower before going into the hot tub. Sweat, perfume, soaps, shampoo and any other oil, chemical or bit of dirt or grime that is attached to you will potentially pollute your hot tub water and increase the risk of bacteria growth. Of course your sanitizer will take care of most of it but giving it a head start can prolong the time between water changes, use less sanitizer chemicals and reduce the possibility of water problems and bad hot tub smells.

Changing the water – If things have got really bad and shock dosing the tub doesn’t get rid of the smell and you are sure that your water chemistry is right then changing the water may be the next thing to try.

Start by using a flushing solution to make sure that the internal plumbing of the hot tub is as clean as it can be. Add the flushing solution to the hot tub before you drain the water according to the instructions and then allow the jets to run for a while to flush out the dirt from the pipework into the water.

Next, switch off the hot tub from the electricity and drain the water out. Once the tub is empty you need to spend a good deal of time and elbow grease ensuring that the hot tub and cover are as spotlessly clean as you can get them. The smell you are suffering from is probably due to bacteria growth and if you don’t get rid of it from the hot tub body then, even with a clean refill of water, it will return.

Once the hot tub is completely clean wash it down with clear water to remove any residual dirt or cleaning solution.

Replace the drain plug and refill the hot tub. Filter the water as you refill through a filter attachment on the hose and then take your time to make sure that the total alkalinity and PH levels are correct before adding sanitizer.

Cleaning the Plumbing – If you have a strange sort of plastic smell coming from the hot tub then you may possibly have a biofilm problem. This is when bacteria clings to the inside of the hot tub’s plumbing.

Luckily this isn’t as difficult to fix as it sounds and it can be done with a flushing solution. Add the flushing solution to the hot tub water before running the jets to flush out all of the gunk.

The water will need to be drained and changed after this process and you will need to give the hot tub shell a good clean down to make sure that all remnants of dirt and bacteria are removed before refilling.

Cleaning the Filters – Filters can become clogged and allow debris and bacteria to multiply in the hot tub’s water. This shouldn’t be a problem if you regularly check and clean them but, even if you do and you have a smell problem then check them anyway.

If you haven’t changed the filter for a long time then it might be a good idea to replace it. You should do this every year anyway but, if you do have a filtration problem it would be worth trying a new filter anyway.

If you have recently changed the filter then give the filter a soak in a cleaning bath for 24 hours and use a hose to thoroughly clean the filter with clear water. Try to get into all of the nooks and crannies and get the filter as clean as possible before replacing it.

If you do a water drain and change you should always thoroughly clean or replace your filter at the same time.

Drying out the Cover – I have written a detailed post on how to dry out a hot tub cover here but I will include a quick version in this post as well.

Your cover will have become waterlogged if it has become old or damaged. Steam will have entered the foam core through the damaged outer cover and, as it condenses in the foam core it turns back to water. The core acts like a giant sponge and just soaks it all up!

To dry the cover out you need to take it off the hot tub and then unzip it. Carefully take out the foam cores and remove the vapor seal from them. This will be a waterproof plastic membrane wrapped around them. Lay the cores out in the sunshine and allow them to dry before reassembling the cover.