Buying a water filter with HSA/FSA dollars discounts it by your tax rate — commonly 20 to 37%. Here is exactly how the math works, worked examples at different prices and brackets, and what changes your real savings.
The short answer
You save your marginal tax rate — typically 20–37%. Because HSA/FSA dollars are pre-tax, an eligible filter effectively costs that much less. On a $2,000 system, that is roughly $400–$740 back.
Money you put into an HSA or FSA is set aside before income tax. When you spend it on a qualified expense, you never pay tax on those dollars — so the effective price drops by your marginal rate. It is not free; you save your tax rate, not 100%. But on a multi-hundred or multi-thousand-dollar purchase, that adds up fast.
| System price | At 22% | At 30% | At 37% |
|---|---|---|---|
| $399 (under-sink RO) | ~$88 saved | ~$120 saved | ~$148 saved |
| $1,170 (whole house) | ~$257 saved | ~$351 saved | ~$433 saved |
| $2,000 (combo) | ~$440 saved | ~$600 saved | ~$740 saved |
Illustrative only — your actual saving depends on your bracket and is not a guarantee.
Pick a system, then pay pre-tax via the TrueMed checkout to capture the discount.
Shop eligible systems →This is not tax advice — confirm your bracket and situation with a professional. For how to actually buy, see how to buy with HSA/FSA.
You save your marginal tax rate, commonly 20-37%. On a $2,000 system that is roughly $400-$740, depending on your bracket and state.
No. You save your tax rate, not the full price. The exception is spending an expiring FSA balance you would otherwise forfeit, which effectively saves 100% of that money.
Often yes. HSA/FSA savings frequently apply at the state level too, and FSA contributions can also avoid payroll tax, increasing the total discount.
