If you own a hot tub, you have probably regretted the extra expense it tacks on to your water bill most months when it is in use.
That first filling and then refilling for periodic cleaning can use hundreds of gallons, to say nothing of topping off for evaporation. It adds up!
But you might have wondered, could you make use of rainwater to fill your hot tub? Will it work, and will it harm the hot tub in any way? Can you really fill a hot tub with rainwater?
Yes, you can fill a hot tub with rainwater, and as long as you ensure the water is free of sediment it will not harm your hot tub. Adding rainwater to existing water will necessitate adjusting the pH balance, however.
If you can pull it off, filling your hot tub with rainwater is a great way to save a bunch of money on water and also be more eco-friendly in the process.
It is really is that simple, and you’ll only need to keep a couple of points in mind for the process. Keep reading and we will tell you what they are.
Rainwater Wills Work Just Fine to Operate a Hot Tub
The water that comes out of your hose or spigot is typically treated with chemicals to make it safe for drinking, but it can also be contaminated by pipes that are old and leach chemicals into the water.
This is not totally ideal for hot tubs, which are built to operate with fresh, clean water only.
Rainwater nominally won’t have that problem, excepting any trace contaminants it picked up from the atmosphere or whatever surface it contacted before you captured it.
If you can collect the rainwater from a clean surface like a new tarp, it will be as good as or better than water from your hose for hot tubs.
That means that in addition to being free (or at least, very cheap), using rainwater can actually be better for your hot tub in terms of water quality.
Just make sure to have a plan for filtering it, if needed, before using it, as we will discuss in the next section.
Make Sure You Pre-Filter if Filling from a Rooftop Rain Catcher
If you’re filling your hot tub completely with rainwater, it is important that you filter it before adding it to the tub.
This is doubly important if you are collecting rainwater from a rooftop rain catcher, as the water will likely have picked up some serious particulates along the way.
While most hot tubs have built-in filters to catch larger pieces of debris, you don’t want to chance any grit or sand getting into and damaging the pump or other working parts of your tub.
The last thing you want is for your relaxing soak to turn into an expensive repair job! Even if the particulates aren’t too much to handle, they will degrade your filters unnecessarily.
A simple pre-filter can be easily made at home with a fine cloth and an elastic band.
Just attach the cloth over a catch container as you pour from one to the other and it will filter out the largest bits and grit.
Be Careful of Sediment if Filling from Rain Barrels
In the same vein, you want to be careful of sediment if you are using rain barrels to fill your hot tub.
Any particulates that manage to get into the barrel will quickly settle to the bottom, so if you aren’t careful when scooping or siphoning water out with a bucket you might end up dumping a bunch of sediment directly into your hot tub.
The best way to avoid this is to pre-filter as explained above, or to be very careful about drawing the water in the first place so you don’t disturb the sediment.
This way, you can slowly and carefully pour the water off the “top” of the barrel into the tub, leaving all the sediment behind sitting on the bottom of the barrel.
Rainwater Added to Existing Water will Alter the pH Balance
If you are only looking to add a little bit of rainwater to your hot tub to top it off, that is perfectly fine and will not present any problems.
However, it is important to note that adding a lot of rainwater (or any new water for that matter) can throw off the pH balance of your hot tub water once it has been treated.
This is because rainwater has a different pH level than your municipal water, and it is definitely different from the water currently in your tub.
Adding too much of it can make the water more acidic or basic than is desired. The same goes for well water or any other type of “natural” water source.
The good news is that this problem is easily remedied by using a test kit to check the pH level after adding the rainwater and then adjusting as needed with a pH up or down product.
These are relatively inexpensive and available at any pool supply store, or even some large hardware stores.
You Can Use a Hot Tub to Hold Emergency Drinking Water in a Pinch
There is another, altogether different reason to consider filling up your hot tub with rainwater.
That is, in an emergency situation where clean drinking water is hard to come by, your hot tub can actually act as a holding tank for safe drinking water.
Having a couple hundred gallons of safe or at least safer water on hand will be a real comfort when times are uncertain and your usual water cannot be trusted. This approach depends on a couple of prerequisites.
First, your hot tub must be drained; you don’t want to drink pool chemicals!
Second, your hot tub should be clean. A badly neglected, scummy hot tub will only contaminate your water source.
Third, you need a way to transfer the rainwater to the hot tub, one way or the other. Lastly, make sure you devise a snug-fitting, opaque cover for the tub to cut down on contamination after it is filled.
As usual, you will want a way to purify your rainwater prior to drinking it, although it should be plenty clean enough for bathing and cleaning purposes.
For drinking, simply draw it and treat it as needed before consumption or storing it in clean containers.
Tom has built and remodeled homes, generated his own electricity, grown his own food and more, all in quest of remaining as independent of society as possible. Now he shares his experiences and hard-earned lessons with readers around the country.