Whole-house and under-sink filters solve different problems. One treats every tap; the other treats your drinking water affordably. Here is how they compare on coverage, cost, and installation — and which makes the stronger HSA/FSA case.
Coverage vs cost
Whole-house for every tap; under-sink for affordable drinking water. Whole-house makes the broader medical-necessity case; under-sink is the budget and renter-friendly choice. Both eligible with a Letter of Medical Necessity.
A whole-house system (point-of-entry) treats water where it enters your home, so every tap, shower, and appliance gets filtered water. An under-sink system (point-of-use) treats one tap — usually the kitchen — for drinking and cooking. The right choice depends on whether your concern is the whole home or just what you drink.
| Whole-house | Under-sink | |
|---|---|---|
| Coverage | Every tap & shower | One tap |
| Typical cost | Higher (from ~$1,000+) | Lower (~$399) |
| Installation | Point of entry (plumber common) | Under one sink |
| Renter-friendly | No | Yes |
| Medical-necessity scope | Broad (e.g. showering, skin) | Drinking water |
Choose whole-house if your concern reaches beyond drinking water — chlorine on skin and hair, a household member with a heightened vulnerability, or whole-home contaminant exposure. It also makes the strongest medical-necessity case because it addresses every point of contact. See whole-house eligibility.
Choose under-sink if your concern is specifically your drinking and cooking water (lead, nitrates, taste), if budget matters, or if you rent. It is the lowest-cost eligible route — see RO eligibility.
Every tap, or just the kitchen — both eligible via the TrueMed checkout with a Letter of Medical Necessity.
Whole-house filter → Under-sink RO →Whole-house treats every tap and makes the broader medical-necessity case; under-sink treats drinking water affordably and suits renters. Choose based on whether your concern is whole-home or drinking-water only.
Under-sink, typically around $399 versus $1,000+ for whole-house. The pre-tax discount applies to either.
Whole-house, because it addresses every point of contact including showering. But under-sink is fully eligible too with a Letter of Medical Necessity.
