Aquatic Therapy Billing Mastery: Navigating CPT 97113 Guidelines in 2026

TLDR: Essential CPT 97113 Aquatic Therapy Billing Rules

CPT 97113 is a time-based code requiring direct, one-on-one contact between therapist and patient—you cannot bill if observing from the pool deck while treating others. Documentation must explicitly justify why the aquatic environment is medically necessary (buoyancy for non-weight bearing, warmth for spasticity) versus land-based therapy. Critical compliance reminders: transition times like dressing and showering are not billable under the 8-minute rule; 97113 is a therapeutic procedure, not a modality, so you cannot bill whirlpool (97022) for the same session; and enforcement agencies have prosecuted practices for scheduling multiple patients simultaneously while billing one-on-one time. Medicare removed 97113 from the Efficiency Adjustment List in 2026, signaling increased scrutiny—making automated billing calculators that handle mixed-remainders logic essential for accurate claims.

Aquatic therapy offers transformative benefits for patients recovering from orthopedic injuries, managing chronic pain, or working through neurological conditions. The buoyancy of water reduces joint stress, while resistance and warmth facilitate therapeutic movement patterns impossible on land. Yet for physical therapy practices offering pool-based rehabilitation, the billing landscape for CPT code 97113 remains one of the most complex—and heavily audited—areas of outpatient therapy reimbursement.

If your practice offers aquatic therapy, understanding the strict compliance requirements surrounding CPT 97113 isn’t optional. Federal enforcement agencies have made aquatic therapy billing a priority target, with six separate law enforcement agencies coordinating investigations into Pennsylvania providers who allegedly billed one-on-one treatment while simultaneously treating multiple patients in the pool.

This comprehensive guide breaks down the critical compliance requirements for billing CPT 97113 in 2026, from medical necessity documentation to the nuances of the 8-minute rule when transition times consume valuable treatment windows.

Understanding CPT 97113: Definition and 2026 Updates

The American Medical Association defines CPT 97113 as “Therapeutic procedure, 1 or more areas, each 15 minutes; aquatic therapy with therapeutic exercises.”

This code encompasses therapeutic exercises, neuromuscular reeducation, gait training, and therapeutic activities performed in pools, Hubbard tanks, whirlpools, and underwater treadmills. The key phrase is “with therapeutic exercises”—passive modalities without active exercise do not qualify for this code.

What Changed in 2026

In the CMS 2026 Medicare Physician Fee Schedule final rule, CPT 97113 was removed from Medicare’s Efficiency Adjustment List. This represents a positive year-over-year reimbursement change after previous reductions, signaling CMS recognition of aquatic therapy’s clinical value.

However, this increased recognition comes with heightened scrutiny. Medicare Administrative Contractors (MACs) have intensified documentation audits to ensure aquatic therapy truly requires the skilled application of therapeutic exercise, not just supervised pool time.

The Non-Negotiable One-on-One Mandate

The most critical compliance requirement for CPT 97113 is direct, one-on-one patient contact throughout the billable treatment time. This isn’t a guideline—it’s a federal billing requirement that has resulted in False Claims Act prosecutions.

What One-on-One Actually Means

According to Medicare billing guidelines, “Aquatic therapy with therapeutic exercise (97113) should not be billed when there is not one-on-one contact between therapist and patient.”

The guidance explicitly states: “An aqua aerobic class of more than one patient with the instructor directing the class from a distance would not be considered reasonable and necessary.”

This means:

• Compliant: A physical therapist is in or beside the pool, providing hands-on resistance, tactile cueing, and direct supervision to a single patient performing therapeutic exercises
• Non-Compliant: A physical therapist supervises three patients from the pool deck, calling out instructions while documenting notes
• Non-Compliant: A therapist rotates among four patients in the pool, spending 5 minutes with each during a 20-minute session, then billing each patient for multiple units

The Pennsylvania Enforcement Case

Federal prosecutors alleged that a physical therapy practice manually altered patient schedules to conceal that Medicare patients were scheduled simultaneously with other patients. The enforcement investigation involved the Department of Health and Human Services Office of Inspector General, FBI, IRS Criminal Investigation, and state authorities—demonstrating how seriously federal agencies treat aquatic therapy billing fraud.

The takeaway: if your scheduling system shows overlapping aquatic therapy appointments, auditors will presume you’re billing for group therapy using one-on-one codes—and the burden of proof falls on you to demonstrate otherwise.

How This Differs from Group Therapy Billing

If you provide aquatic therapy to multiple patients simultaneously, you must use CPT 97150 (Therapeutic procedure(s), group, 2 or more individuals). This code pays significantly less than 97113 because the therapist’s attention is divided.

Some practices attempt to bill a “group of one” using 97150 when scheduling constraints result in solo sessions, but this often triggers audits. Medicare expects 97113 for individual treatment and 97150 only when multiple patients are genuinely present. For more details on navigating these distinctions, see our guide on group therapy billing in physical therapy.

Medical Necessity: Proving Why Water Matters

Simply documenting that a patient performed therapeutic exercises in the pool is insufficient. You must justify why the aquatic environment is medically necessary for this specific patient’s condition—in other words, why land-based therapy would be less effective or contraindicated.

What Qualifies as Medical Necessity

Novitas Solutions MAC guidance states that aquatic therapy may be considered medically reasonable and necessary when:

• The patient cannot perform land-based exercises effectively to treat their condition without first undergoing aquatic therapy
• Aquatic therapy facilitates progression to land-based exercises
• Specific therapeutic properties of water (buoyancy, resistance, warmth, hydrostatic pressure) address documented functional limitations

Documentation Requirements That Demonstrate Medical Necessity

Your evaluation and treatment notes must explicitly connect the aquatic environment to the patient’s clinical presentation. Strong documentation includes:

1. Objective functional deficits: “Patient demonstrates 3+/5 quadriceps strength with inability to tolerate weight-bearing knee extension exercises on land due to pain rated 8/10. Buoyancy-assisted exercise in pool reduces pain to 3/10, allowing therapeutic loading through full ROM.”

2. Specific aquatic properties utilized: “Warm water temperature (92°F) reduces lower extremity spasticity (Modified Ashworth Scale 3 → 1+), enabling functional gait pattern training not achievable in clinic.”

3. Progression rationale: “Patient previously demonstrated fall risk during land-based balance activities (Berg Balance Scale 38/56). Aquatic environment provides safer progression of dynamic balance challenges with reduced fall consequence.”

4. Why land-based alternatives are insufficient: “Patient’s 320 lb body weight and bilateral knee OA preclude therapeutic weight-bearing exercise on land. Aquatic buoyancy reduces effective weight to 30%, enabling squat pattern retraining.”

What Doesn’t Qualify

According to CMS guidelines, these scenarios are non-covered:

• “Exercises in the water environment to promote overall fitness, flexibility, improved endurance, aerobic conditioning, weight reduction, or for maintenance purposes”
• General pool therapy without therapeutic exercises (e.g., whirlpool for wound care)
• Aquatic exercise programs that could be performed on land with equal effectiveness

Every 10 Visits: Enhanced Documentation Standards

NGS (National Government Services) and other MACs require enhanced supportive documentation at least every 10 visits for CPT 97113. This must include:

• Objective measures of functional loss (ADLs, mobility, ROM, strength, balance, coordination, posture)
• Specific exercises/activities performed with progression details
• Purpose of exercises related to functional outcomes
• Instructions given and assistance level needed
• Clear demonstration that skilled therapy judgment was required

Missing this enhanced documentation is one of the most common audit triggers for aquatic therapy denials.

The 8-Minute Rule: What Counts as Billable Time

CPT 97113 is a time-based code billed in 15-minute increments according to Medicare’s 8-minute rule. This creates a critical challenge for aquatic therapy: how do you account for the non-billable transition time that consumes every pool therapy session?

Understanding Time-Based Billing for Aquatic Therapy

Under the 8-minute rule, you can bill:

• 1 unit for 8-22 minutes of direct treatment
• 2 units for 23-37 minutes
• 3 units for 38-52 minutes
• 4 units for 53-67 minutes (Note: Some MACs limit aquatic therapy to 4 units per day)

The challenge: CMS explicitly states that “the aquatic therapy treatment minutes counted toward the total timed code treatment minutes should only include actual skilled exercise time that required direct one-on-one patient contact by the qualified professional/auxiliary personnel. Do not include minutes for the patient to dress/undress, get into and out of the pool, etc.”

The Transition Time Problem

A typical 60-minute aquatic therapy appointment includes:

• 5 minutes: Patient changes into swimwear
• 3 minutes: Therapist escorts patient to pool, safety briefing
• 2 minutes: Patient enters pool via lift or stairs
• 38 minutes: Direct therapeutic exercise with one-on-one contact ✓ BILLABLE
• 3 minutes: Patient exits pool, towels off
• 5 minutes: Patient changes back into street clothes
• 4 minutes: Post-treatment discussion, home exercise review

Total billable time: 38 minutes = 2 units of 97113

Many practices mistakenly bill the full 60-minute appointment (3 units), triggering audits when reviewers compare scheduled time blocks to documented treatment time.

The Mixed-Remainders Challenge

When you provide multiple timed codes in the same session (e.g., therapeutic exercise on land before pool therapy), calculating total billable units becomes mathematically complex. If a patient receives:

• 18 minutes of therapeutic exercise (97110) on land
• 28 minutes of aquatic therapy (97113) in the pool

The total time is 46 minutes, which equals 3 units total under the 8-minute rule. But how do you allocate those 3 units between the two codes? This “mixed-remainders” problem is where automated 8-minute rule calculators become essential—and where billing errors frequently occur in manual calculations.

Proactive Chart’s Automated Solution

This is precisely where modern EMR systems designed for therapy practices outperform generic medical record platforms. Proactive Chart’s built-in 8-minute rule calculator automatically:

• Tracks only direct treatment time for each CPT code
• Excludes transition activities from billable calculations
• Handles mixed-remainders logic when multiple timed codes are used
• Alerts therapists when documented time doesn’t support billed units
• Provides real-time unit calculations during documentation

For aquatic therapy practices, this automation eliminates the most common source of billing errors—and provides audit-proof documentation showing exactly how billable units were calculated.

CPT 97113 vs. 97022: The Modality Billing Prohibition

One of the most misunderstood aspects of aquatic therapy billing is the relationship between CPT 97113 (aquatic therapy with therapeutic exercise) and CPT 97022 (whirlpool therapy).

The Core Rule: You Cannot Bill Both

CMS guidelines explicitly state: “Do not bill for the water modality used to provide the aquatic environment, such as whirlpool (97022), in addition to 97113.”

Here’s why: CPT 97113 is a therapeutic procedure requiring skilled therapeutic exercise. CPT 97022 is a modality—a passive physical agent applied to the patient.

When you provide therapeutic exercises in water, the aquatic environment itself is already bundled into the 97113 code. Billing 97022 separately constitutes duplicate billing for the same aquatic environment.

What Qualifies as 97022 (Whirlpool)

CPT 97022 is appropriate only when the patient is receiving passive whirlpool therapy without therapeutic exercise. For example:

• Pre-exercise warm-up using whirlpool agitation (no active exercise)
• Wound debridement in whirlpool (without concurrent therapeutic exercise)
• Contrast baths for edema management (passive modality)

If the patient performs any therapeutic exercises during the aquatic session, you’re in 97113 territory—and 97022 is no longer separately billable.

The “Coding Around” Fraud Risk

Multiple Medicare contractors warn that “billing for aquatic physical therapy using codes other than 97113 is fraudulent and referred to as ‘coding around.’”

Some practices attempt to unbundle aquatic therapy by billing:

• 97022 (whirlpool) for the aquatic environment
• 97110 (therapeutic exercise) for the exercises performed

This is incorrect. When therapeutic exercise occurs in an aquatic environment, 97113 is the only appropriate code. Deliberately using other codes to avoid 97113’s documentation requirements or to manipulate reimbursement is considered fraudulent billing.

Common Compliance Pitfalls and How to Avoid Them

Drawing from enforcement cases and MAC audit findings, these are the most frequent CPT 97113 billing errors:

1. Overstating Billable Time by Including Transitions

The Problem: Billing for the full appointment slot rather than actual hands-on treatment time.

The Solution: Use precise start/stop times in documentation. “Aquatic therapy start: 10:14 AM (patient entered pool), end: 10:46 AM (patient exited pool). Total direct treatment: 32 minutes = 2 units.”

2. Billing One-on-One Rates for Overlapping Schedules

The Problem: Scheduling multiple patients in the pool simultaneously and billing 97113 for each.

The Solution: If your practice model involves multiple patients, use CPT 97150 (group therapy). If you genuinely provide one-on-one care with overlapping appointments (e.g., therapist A with patient 1, therapist B with patient 2), document which therapist provided which service.

3. Inadequate Medical Necessity Documentation

The Problem: Notes state “Patient performed aquatic therapy exercises” without justifying why the pool environment was clinically necessary.

The Solution: Every aquatic therapy note should include at least one sentence explaining the therapeutic rationale: “Aquatic buoyancy essential to reduce axial loading on post-surgical lumbar spine, enabling core stabilization exercises not tolerable on land.”

4. Missing Required Modifiers

The Problem: Submitting claims without appropriate therapy modifiers (GP for physical therapy, CQ for PTA services).

The Solution: Configure your billing system to require modifiers before claims can be submitted. Missing modifiers are among the most common causes of aquatic therapy claim denials.

5. Exceeding MAC-Specific Unit Limits

The Problem: Billing more units than your MAC allows per day.

The Solution: Know your MAC’s specific limits. CGS, for example, limits aquatic therapy to 4 units per day, per discipline. Billing 5 units will trigger an automatic denial.

6. Using Non-Qualified Personnel

The Problem: Having exercise physiologists, kinesiotherapists, or techs provide aquatic therapy.

The Solution: CPT 97113 requires a licensed physical therapist or physical therapist assistant under appropriate supervision. Non-licensed personnel cannot perform or bill for aquatic physical therapy services.

Building an Audit-Proof Aquatic Therapy Compliance Program

Given the heightened enforcement focus on aquatic therapy billing, your compliance program should include these specific safeguards:

Documentation Templates with Built-In Compliance Prompts

Create aquatic therapy-specific note templates that require therapists to address:

• Medical necessity statement (why aquatic vs. land-based)
• Specific water properties utilized (buoyancy, resistance, warmth, pressure)
• Precise start/stop times for in-pool treatment
• One-on-one confirmation (therapist signature attesting to exclusive patient contact)
• Objective functional measures every 10 visits

Scheduling System Audits

Regularly review your scheduling software for:

• Overlapping aquatic therapy appointments (red flag for one-on-one billing)
• Appointment duration vs. billed units (60-minute slots shouldn’t automatically generate 4 units)
• Therapist-to-patient ratios during pool time blocks

Staff Training on Transition Time Exclusions

Many therapists don’t realize that the time they spend helping a patient safely enter and exit the pool cannot be billed. Create clear training materials showing:

• What activities count toward billable time (hands-on exercise, tactile cueing, resistance, manual techniques)
• What activities don’t count (safety briefings, equipment setup, patient changing, entering/exiting pool)

Automated Billing Calculations

Human error in 8-minute rule calculations is common, especially when multiple timed codes are involved. EMR systems with built-in therapy billing logic eliminate this risk while providing documentation that shows exactly how units were calculated—critical during audits.

Proactive Chart’s system specifically addresses aquatic therapy workflow by:

• Allowing therapists to mark “transition time” separately from treatment time
• Auto-calculating maximum billable units based on documented direct contact time
• Flagging claims that exceed MAC-specific daily limits
• Generating audit trails showing unit calculation logic

Quick Reference: CPT 97113 Billing Compliance Checklist

Use this checklist before submitting aquatic therapy claims:

Why Aquatic Therapy Billing Expertise Matters

The therapeutic benefits of aquatic rehabilitation are well-documented: reduced joint stress, improved ROM, enhanced neuromuscular control, and pain reduction through warmth and buoyancy. For many patients—particularly those with severe arthritis, post-surgical weight-bearing restrictions, or neurological conditions—pool therapy represents the difference between therapeutic success and plateau.

But these clinical benefits mean nothing if improper billing triggers audits, claim denials, or worse—fraud investigations. The enforcement actions targeting aquatic therapy providers send a clear message: Medicare is scrutinizing this service line with particular intensity.

The practices that thrive with aquatic therapy programs share common traits:

• Precise documentation that explicitly justifies medical necessity
• Scheduling systems that prevent overlapping appointments when billing one-on-one codes
• Staff training emphasizing what counts as billable time
• Technology solutions that automate 8-minute rule calculations and flag potential compliance issues

How Proactive Chart Supports Aquatic Therapy Excellence

Proactive Chart was built by clinicians who understand the unique challenges of therapy billing—including the complexity of CPT 97113 compliance. Our platform provides:

Intelligent 8-Minute Rule Calculator

Automatically calculates billable units based on documented treatment time, handles mixed-remainders when multiple codes are used, and alerts therapists when billed units don’t match documented time. This is particularly crucial for aquatic therapy, where transition time creates frequent calculation challenges.

Aquatic Therapy-Specific Workflows

Document start/stop times for in-pool treatment separately from total appointment time, ensuring your billed units reflect only direct therapeutic exercise—not dressing, showering, or pool entry/exit time.

Built-In Compliance Safeguards

Flags missing medical necessity statements, alerts when scheduling shows overlapping appointments with one-on-one billing, and warns when claims exceed MAC-specific daily unit limits for 97113.

Audit-Ready Documentation

Generates reports showing exactly how billable units were calculated for each service date—essential when defending claims during audits. Every claim includes a clear audit trail from documented time to billed units.

Medical Necessity Prompts

Customizable note templates ensure therapists address the critical question: “Why is the aquatic environment medically necessary for this patient?” Templates can include diagnosis-specific medical necessity language to streamline documentation.

Conclusion: Precision in Aquatic Therapy Billing Protects Your Practice

CPT 97113 offers appropriate reimbursement for skilled aquatic therapy services—but only when billed correctly. The one-on-one requirement, medical necessity documentation, 8-minute rule application, and modality billing prohibitions create a complex compliance landscape where even well-intentioned errors can trigger audits.

The 2026 removal of CPT 97113 from Medicare’s Efficiency Adjustment List signals increased recognition of aquatic therapy’s value. But this opportunity comes with responsibility: as reimbursement improves, audit scrutiny intensifies. Federal enforcement actions demonstrate that agencies are actively investigating aquatic therapy billing patterns, particularly around one-on-one requirements.

The solution isn’t to avoid offering aquatic therapy—it’s to bill it correctly. That means:

• Document with precision: Justify medical necessity, record exact treatment times, exclude transitions
• Schedule strategically: Avoid overlapping appointments when billing one-on-one codes
• Calculate accurately: Use automated tools for 8-minute rule logic
• Train continuously: Ensure all staff understand what counts as billable time

For practices ready to modernize their billing infrastructure with technology built specifically for therapy compliance, Proactive Chart offers the precision tools that transform aquatic therapy from a compliance risk into a sustainable service line.

Schedule a demo to see how automated 8-minute rule calculations, built-in compliance safeguards, and aquatic therapy-specific workflows can protect your practice while maximizing appropriate reimbursement for this valuable treatment modality.

Sources

• CPT Code 97113: 6 Aquatic Therapy Billing Secrets for Higher Reimbursement
• Enforcement Efforts Targeting Aquatic Therapy Providers and CPT Code 97113 Claims
• CMS Article - Billing and Coding: Outpatient Physical and Occupational Therapy Services
• Aquatic Therapy CPT Code | 97113 | Guidelines
• CMS Releases Medicare Physician Fee Schedule Final Rule for CY 2026
• CPT Code 97113