Is it best to fill my hot tub with hard or soft water for the first time of the season? I have a resin-based water softener that we use in our RV that will bring the water going into it to zero grains of hardness, or should I use untreated water out of the faucet? I plan to use the Bromine method for balancing and maintaining the spa this season and wanted to know which water source would be the easiest to work with.
Soft or Hard water for a spa fill?
- Thread starter JLA956
- Start date
reggiehammond
Gold Supporter
- Oct 4, 2020
- 1,609
- Pool Size
- 30000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
Depends how hard your water is. All the hardness that resin pulls out gets replaced by sodium + chloride ions (or potassium + chloride ions if you use KCl softener salt). If I fill with softened water, I have to add calcium to get the CH up where I want it, so I'm just adding back what was removed and there's a bunch of excess Na / Cl in there that I don't need. I fill with 1/3rd RO/DI water and 2/3rd unsoftened water. I still have to add a little bit of calcium, but I don't have the residual other salts sitting in there bringing up the overall TDS.
I use the RO/DI because the municipal water here is has a lot of alkalinity and it reduces the overall amount of acid I have to add to get the pH in check. Test your tap water, both softened and unsoftened. Are the parameters decently close to where you want the hot tub after balancing? Maybe you even want to use half and half to get things in line.
I use my fairly hard municipal water, and end up adding CH to it.
I add CH to keep foaming down when I use AquaClarity.
I add CH to keep foaming down when I use AquaClarity.
I just tested the tap water and it is approximately 250 ppm which I understand indicates hard water. So, I should go ahead and fill the tub with this tap water and then adjust the pH to the required level? By the way - the softener that I have utilizes no salt at all - it is resin-based although I'm not sure what makes up the resin. Here is a link to the model we have - On The Go Water Softener. Although we bought this to use in our RV, it's interesting to note in the description that they say it works great for spas.
250ppm is a near-perfect amount of calcium hardness to have in a spa. I would stick with unsoftened water unless it is very inconvenient to bypass the softener. Are you sure about the "utilizes no salt at all" part? From the page you linked - "It simply regenerates with 2 boxes of common table salt in less than 30 minutes, and provides the owner with soft water up to 1600 gallons (or up to ~40 days)." Generally the ion exchange resins adsorb calcium and magnesium ions, then when recharged with salt the sodium ions are preferentially adsorbed onto the resin, displacing the Ca/Mg that are washed away in a backwash cycle, then the sodium is exchanged for Ca / Mg during use, and then the cycle repeats.
I think you'll be fine with either softened or unsoftened water, just plan on re-adding enough calcium to get back up above 200ppm if you fill with softened water.
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I run my tub between 300-350 ppm of CH. If you don't get foaming from anything, 250 ppm is just fine.