TL;DR: The Centers for Medicare & Medicaid Services modified NCD 193 governing water purification and softening systems for home dialysis, with an effective date of March 7, 2026. Here's what changes for your billing team.
CMS water purification and softening system coverage policy under NCD 193 Medicare has been updated. This policy controls which water treatment systems qualify as covered durable medical equipment for patients on home hemodialysis or peritoneal dialysis. No specific CPT or HCPCS codes are listed in the updated policy document — but the coverage criteria themselves are detailed and directly shape your medical necessity documentation and claim denial risk.
| Field | Detail |
|---|---|
| Payer | CMS |
| Policy | Water Purification and Softening Systems Used in Conjunction with Home Dialysis |
| Policy Code | NCD 193 |
| Change Type | Modified |
| Effective Date | 2026-03-07 |
| Impact Level | Medium |
| Specialties Affected | Nephrology, Home Dialysis Programs, DME Suppliers, End-Stage Renal Disease (ESRD) Facilities |
| Key Action | Review medical necessity documentation for all home dialysis water systems before billing MACs for coverage after March 7, 2026 |
CMS Home Dialysis Water Purification Coverage Criteria and Medical Necessity Requirements 2026
NCD 193 is the National Coverage Determination governing Medicare coverage of water purification and softening systems for home dialysis use. The Centers for Medicare & Medicaid Services cover these systems under the Home Dialysis Supplies and Equipment benefit category. The core principle hasn't changed — water used for home dialysis must be chemically free of heavy trace metals and organic contaminants. It also needs to be as free of bacteria as possible, though biological sterility is not required.
Two types of water purification systems meet Medicare's coverage standard:
| # | Covered Indication |
|---|---|
| 1 | Deionization — removes organic substances, mineral salts of magnesium and calcium, fluoride compounds, and chloride from tap water through filtration and ion exchange |
| 2 | Reverse Osmosis (RO) — uses pressure to force water through a porous membrane to remove impurities |
Either system alone is sufficient for safe home dialysis. That matters for billing. CMS has determined that using both a deionization unit and an RO unit in series is medically unnecessary. If your patient's physician prescribes both, document clearly why the single-system standard doesn't apply — or expect a claim denial.
Activated carbon filters get their own carve-out. When used as a component of a water purification system to remove unsafe concentrations of chlorine or chloramines, they're covered. The requirement: a physician must prescribe them. Make sure that prescription is in the record before you bill.
Water softening systems are a different story. The default position under this coverage policy is exclusion. CMS does not consider a standalone water softening system reasonable and necessary under §1862(a)(1) of the Social Security Act. The reason is practical — softeners don't remove hazardous heavy metals like arsenic.
A water softening system is covered in one narrow scenario. All three of these conditions must be met:
| # | Covered Indication |
|---|---|
| 1 | The RO unit manufacturer has set specific water quality standards for incoming water |
| 2 | The patient's water supply falls below those standards |
| 3 | The softener is used only to pretreat water entering the RO unit — and only for dialysis |
The softener doesn't have to be physically built into the RO unit. But it must function as an integral part of the dialysis system, not as a general household water treatment device. Document this explicitly. If the MAC questions reimbursement, this is the first thing they'll check.
CMS Home Dialysis Water Softening and Purification Exclusions and Non-Covered Indications
Standalone water softening systems are excluded from Medicare coverage as the default position. The policy is direct: a water softener alone does not adequately remove hazardous heavy metal contaminants like arsenic, so it doesn't meet the reasonable and necessary standard.
Spare deionization tanks are also not covered. CMS classifies them as a precautionary supply, not a current treatment requirement. Don't bill for them. If your DME supplier has been including spare tanks in home dialysis setups, stop now.
Dual-system configurations — running both a deionization unit and an RO unit in series — are considered medically unnecessary. The rationale is that either system independently provides chemically and bacteriologically acceptable water for home dialysis. Billing for both will draw scrutiny from your Medicare Administrative Contractor.
General household water softening is not a covered use under any reading of this policy. The softener must be dedicated to the dialysis system. If there's any ambiguity in the documentation about how the softener is used, the MAC will likely deny the claim.
Coverage Indications at a Glance
| Indication | Status | Relevant Codes | Notes |
|---|---|---|---|
| Deionization water purification system for home hemodialysis or peritoneal dialysis | Covered | No specific codes listed in policy | Standard single-system coverage; physician order required |
| Reverse Osmosis (RO) water purification system for home hemodialysis or peritoneal dialysis | Covered | No specific codes listed in policy | Standard single-system coverage; physician order required |
| Activated carbon filter as component of water purification system (chlorine/chloramine removal) | Covered | No specific codes listed in policy | Physician prescription required |
| Water softening system as pretreatment for RO unit | Covered (conditional) | No specific codes listed in policy | All three manufacturer-standard criteria must be met; must be integral to dialysis system only |
| Deionization unit AND RO unit used together in series | Not Covered | No specific codes listed in policy | Deemed medically unnecessary; either system alone is sufficient |
| Spare deionization tanks | Not Covered | No specific codes listed in policy | Classified as precautionary supply, not current treatment requirement |
| Standalone water softening system (not paired with RO unit) | Not Covered | No specific codes listed in policy | Does not remove heavy metals; excluded under §1862(a)(1) |
| Water softening system used for general household water (not dedicated to dialysis) | Not Covered | No specific codes listed in policy | Must be integral to dialysis system only |
| Water purification system replacing existing water softener — medical necessity not established | Not Covered / MAC Review | No specific codes listed in policy | MAC requires physician to document reason for replacement; scrutiny applies |
CMS Home Dialysis Water Purification Billing Guidelines and Action Items 2026
This is a modified coverage policy, not a new one. The criteria have been clarified and tightened. Your documentation practices need to match the policy as it stands on and after March 7, 2026.
| # | Action Item |
|---|---|
| 1 | Audit your active home dialysis water system claims now. Pull any open or pending claims for home dialysis water treatment equipment. Check each one against the three coverage categories: deionization-only, RO-only, or softener-as-RO-pretreatment. Anything else needs a clinical justification in the chart. |
| 2 | Get physician documentation for every activated carbon filter. The coverage policy requires a physician prescription specifically for activated carbon filters. If your billing team has been treating these as bundled components without separate physician orders, close that gap before March 7, 2026. |
| 3 | Document the three-part test for any water softening system claims. For every softener you bill as covered, the record must show: (a) the RO manufacturer's water quality standards, (b) lab or test results showing the patient's water doesn't meet those standards, and (c) confirmation the softener is used only for dialysis. A missing piece in any one of these three will get the claim denied. |
| 4 | Stop billing for dual deionization-plus-RO systems without a documented exception. CMS considers this medically unnecessary by default. If a physician has a specific clinical reason to prescribe both systems in series, document it in detail. Absent that, don't bill it. Your MAC will deny it on medical necessity grounds. |
| 5 | Flag cases where a water purification system is replacing an existing water softener. NCD 193 calls out this specific scenario as requiring careful medical necessity development. When a purification system replaces a softener in an existing home dialysis setup, the MAC expects the physician to document why. Changes in clinical standards, deteriorating water quality, or prior inability to pay for a purification system are all recognized reasons — but they must be in the record. If your billing team surfaces one of these cases, loop in your compliance officer before submitting the claim. |
| 6 | Verify that spare deionization tanks are not being billed. Check your DME supplier agreements and charge capture setups for any line items related to backup or spare deionization tanks. These are not covered. If your charge capture includes them, remove the line item. |
| 7 | Confirm your MAC's local policies align with NCD 193. NCD 193 sets the national standard, but your Medicare Administrative Contractor may have a local coverage determination that adds requirements or documentation specifics on top of it. Pull your MAC's LCD on home dialysis supplies and confirm there are no additional prior authorization requirements in your jurisdiction before the effective date of March 7, 2026. |
| Previous Version | Current Version |
|---|---|
| Coverage is considered experimental and investigational for all indications | Coverage is considered medically necessary when specific criteria are met |
| Prior authorization is not required | Prior authorization is required for initial treatment |
| Documentation must include clinical history | Documentation must include clinical history |
| Re-review every 24 months | Re-review every 12 months with updated clinical documentation |
CPT, HCPCS, and ICD-10 Codes for Home Dialysis Water Systems Under NCD 193
Covered CPT and HCPCS Codes
The updated NCD 193 policy document does not list specific CPT or HCPCS codes. This is not unusual for older National Coverage Determinations — the coverage criteria govern billing, but the specific billing codes for home dialysis water purification equipment are typically assigned at the HCPCS Level II DME fee schedule level and administered through your MAC.
Contact your MAC or your DME billing specialist to confirm the current applicable HCPCS codes for:
- Deionization systems for home dialysis
- Reverse osmosis systems for home dialysis
- Activated carbon filtration components
- Water softening systems used as RO pretreatment
Do not use codes your team has assumed apply without MAC confirmation. Home dialysis billing is a high-audit area. Guessing codes here creates claim denial exposure that compounds quickly across a patient population.
Key ICD-10-CM Diagnosis Codes
No ICD-10-CM codes are specified in the NCD 193 policy document. End-Stage Renal Disease diagnosis codes should accompany any home dialysis equipment claim. Work with your clinical documentation team to confirm the correct ESRD diagnosis codes are present on every claim before submission.
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