Filling a hot tub in St. Peters raises a question many homeowners do not think about until the spa is already on its pad: should the tub be filled with softened water, with untreated tap water, or with a mix? The answer depends on the tub, the sanitizer you plan to use, and what your home water looks like. This guide walks through the choices in plain terms so you can decide what to check next.
What the local water report tells you
Public water reports for St. Peters describe the tap water as hard, which means it carries more dissolved calcium and magnesium than soft water does. Those minerals are why hard water leaves scale on heating elements and surfaces. The same reports also list items such as high chloride and sodium levels, along with disinfection byproducts that can appear in treated supply. If your home has a softener, it removes hardness minerals and adds sodium in their place. Your report describes the public supply, not necessarily what leaves your softener after it regenerates, so treat it as a starting point.
Softened water in a hot tub: the usual concerns
Hot tubs have their own water chemistry needs, and the two main ones are sanitizer level and water balance. Softened water is often easier on scale, since less calcium is available to deposit on heaters and jets, and many owners find that a real benefit. The trade-off is that softened water carries added sodium, which can raise total dissolved solids in the tub over time. Some owners and service staff watch that number closely. Nothing here is a reason to avoid softened water, but it is a reason to test rather than assume.
Options to weigh
- Fill with softened water, then test the balance after the first fill and after a few days of normal use.
- Fill from a separate line that bypasses the softener, if your plumbing has one, and rely on a sanitizer and balance routine suited to hard water.
- Check the hot tub maker's manual for the fill water it expects, and follow that guidance over general advice.
- Use an outside source for the fill only if the manufacturer's manual allows it.
Testing before you fill
A simple home test kit can measure several things that matter for a hot tub, including total alkalinity, pH, calcium hardness, and sanitizer level. Test your St. Peters tap water and, if your home has one, your softened water, so you can compare the two. If your kit or a lab report also gives sodium or total dissolved solids, record those too. Write down the date and the source for each result, so you know exactly which water you tested.
A practical sequence
- Read the hot tub manual's section on fill water and note any limits it gives.
- Find out which line feeds the spa, and whether that line passes through the softener.
- Test the water you plan to use before the first fill.
- Fill the tub, then test again after circulation and heating have run.
- Write down what you found and adjust your routine from there.
When to ask a professional
If your tests keep drifting, or the water shows scale or cloudiness despite regular care, bring your records to the hot tub maker's service channel or to a qualified local service provider. Describe your water source, whether it is softened, and what your test results show. A clear written record makes that conversation faster and more useful for everyone involved.
Keep in mind
Water chemistry shifts with the seasons, with heavy use, and with the source you draw from. A test you ran last spring may not describe the water in your tub now. Treat hot tub water like the rest of your home water: check it on a regular schedule, and keep a simple log of what you see.