CPT code 97113: Aquatic therapy billing and coding guide

Key takeaways

CPT code 97113 covers aquatic therapy with therapeutic exercises, billed per 15-minute unit of one-on-one care.

Only skilled treatment minutes count, so changing, pool entry, and drying off never reach the claim.

Medicare Part B covers 97113 when the note explains why water suits this patient better than land.

Same-day billing with 97110 turns on documentation of two distinct services, not on a modifier rule.

Practice management software like Pabau pre-fills claims from the visit record and flags missing required fields.

CPT code 97113 covers aquatic therapy with therapeutic exercises, billed per 15-minute unit of one-on-one care. One rule decides most claims. Only the minutes a therapist spends treating the patient in the water count toward those units.

Payers read this code closely, because a pool session looks a lot like recreational fitness on paper. A note that reads like an exercise log comes back denied. So three questions decide the claim: who may bill, what the record proves, and which minutes count.

What CPT code 97113 actually pays for

The American Medical Association (AMA) publishes the official descriptor for 97113. It reads: Therapeutic procedure, 1 or more areas, each 15 minutes; aquatic therapy with therapeutic exercises. The AMA maintains the CPT code set, so its wording settles any question of interpretation.

Aquatic therapy uses buoyancy, water resistance, and hydrostatic pressure to make exercise possible when land-based work would hurt too much. Swimming lessons and recreational hydrotherapy do not qualify. The therapeutic exercise is what separates 97113 from a non-covered pool session, and the notes have to say so plainly.

Who can bill 97113, and who cannot

Eligibility rests on two things: state licensure and payer policy. Under Medicare, these provider types may bill the code.

• Physical therapists (PT) – the primary biller, working independently or under physician supervision depending on the setting
• Occupational therapists (OT) – eligible when aquatic therapy sits inside the OT treatment goals
• Physical therapist assistants (PTA) – may deliver the service under PT supervision, with a 15% Medicare payment reduction applied
• Occupational therapy assistants (OTA) – same arrangement as PTAs, and the same 15% reduction
• Physicians and non-physician practitioners – may bill when they perform the service themselves, which is uncommon in a pool

Speech-language pathologists sit outside this code under most payer policies, since aquatic therapy falls outside typical SLP scope. State licensure rules vary too, so check your state board’s scope-of-practice language before you build a pool-based service line. Your Medicare Administrative Contractor (MAC) can confirm the rest.

Medicare covers 97113, on its own terms

Medicare Part B pays for 97113 as an outpatient therapy service when the care is medically necessary. The patient also has to be expected to improve within a reasonable timeframe. Coverage sits under the Medicare Benefit Policy Manual, Chapter 15, and each MAC adds its own Local Coverage Determinations (LCDs).

Underneath all of that is one expectation. The record has to explain why this patient needs water rather than a mat and a set of bands.

What makes water medically necessary

Medical necessity turns on a therapeutic advantage the patient cannot get on land. These conditions usually clear that bar:

• Severe weight-bearing restrictions after surgery or a fracture
• Significant pain during land-based therapeutic exercise
• Neurological conditions affecting balance or motor control
• Severe obesity limiting tolerance for ground-level exercise
• Burns or skin conditions that rule out land-based therapy

What 97113 pays in 2026

Reimbursement moves with geographic locality and place of service. The CMS Physician Fee Schedule lookup tool gives current rates by zip code and provider type. The figures below are approximate national averages for 2026, so treat them as a starting point rather than a quote.

Rates shift with each annual fee schedule update, so check CMS before you build them into a forecast.

KX is a claim you have to back up

Medicare sets an annual threshold on outpatient therapy spending, indexed each year. Once a patient’s combined physical therapy and speech services pass it, treatment can continue if it remains medically necessary. The KX modifier is how the therapist says exactly that, and points to a record that supports it.

Using KX early is an audit trigger. Append it only after the patient has passed the threshold for the year. The documentation behind it has to show why care continues, in clinical terms rather than habit.

The 8-minute rule decides your units

97113 is a time-based code billed in 15-minute increments. Under the CMS 8-minute rule, one unit needs at least eight minutes of direct skilled service. More units need proportionally more time, on the ladder below.

Here is where aquatic therapy differs from every other code on that ladder. Pool entry, changing, and drying off are part of the visit, but none of it is treatment. Only the minutes of skilled therapeutic exercise in the water go into the total. That difference usually costs a session one unit.

Place of service matters just as much. Use 11 for a private practice pool and 22 for hospital outpatient. Code 12 belongs only to services delivered in the patient’s home. Pick the wrong one and you land on the wrong side of the facility rate.

The modifiers that belong on a 97113 claim

Which modifiers you need depends on provider type, payer, and what happened in the session.

Notes that prove skilled care, not a swim

Thin documentation is the leading cause of 97113 denials and post-payment recoupments. Every billed session needs contemporaneous notes that show skilled care. A standard template keeps the required elements in front of the therapist while they write.

Required elements include:

• Evaluation and plan of care: signed by the supervising therapist, with diagnosis, functional deficits, goals, frequency, and duration
• Medical necessity justification: the clinical reason aquatic therapy beats a land-based alternative for this patient
• Treatment notes per session: date, exercises performed, body area treated, minutes of direct contact, and patient response
• Progress notes: reassessment every 10 visits or 30 days under Medicare, measured against the goals
• One-on-one contact: notes that reflect continuous attendance, since group aquatic exercise cannot be billed as 97113
• Therapist signature: every note signed and dated by whoever rendered or supervised the service

Read a finished note back and ask one question. Does it describe a clinician making decisions, or a patient doing exercises? The first gets paid.

Which ICD-10 codes support a 97113 claim

Every 97113 claim needs a supporting ICD-10-CM diagnosis, and the diagnosis has to make the case for water. The CDC/NCHS ICD-10-CM web tool confirms the current code set. These pairings come up most often:

One trap catches practices every year. ICD-10 code M54.5 was retired in October 2021, so a claim carrying it rejects on arrival. Use M54.50, or a more specific low back pain code where the record supports one.

Why 97113 claims get denied

Aquatic therapy denies more often than most outpatient therapy codes, for a straightforward reason. Payers are watching for pool time dressed up as treatment. These six patterns account for most of it.

• No medical necessity statement: the record never says why water beats land for this patient. Add one or two explicit sentences to each plan of care update.
• Group session billed as individual: 97113 needs one-on-one contact. Two patients in the pool with one therapist means neither visit qualifies, so bill CPT 97150 instead.
• Transition time in the unit count: entry, changing, and exit inflate the total. Track active treatment minutes separately from session length.
• Same-day 97110 without distinct documentation: no edit blocks the pair. What payers want is a note showing two separate services, with the minutes for each recorded on its own.
• Missing GP or GO modifier: every Medicare outpatient therapy claim needs the discipline modifier. Without it, the claim rejects automatically.
• Retired diagnosis code: M54.5 in place of M54.50 rejects immediately. Check your favorites list against the current ICD-10-CM release each October.

Patterns beat one-off corrections here. Track which denial codes keep coming back, then fix the note template that produced them. A claim denied for thin documentation in March gets denied again in June if only the claim was corrected.

Before you submit: the five-point check

Four fields decide whether a 97113 claim survives its first pass. They are the diagnosis, the units, the modifiers, and the plan of care date. Your clearinghouse checks the format first, then the payer’s system checks policy rules. Nobody reads the clinical note unless the claim reaches review or appeal.

That order is why a two-minute check before submission beats a two-week appeal after one. Run through these five:

• Minutes: the note records skilled treatment time only, with changing and pool entry left out
• Units: the minute total sits inside the band you billed, not the length of the visit
• Modifiers: GP or GO for the discipline, plus CQ or CO if an assistant delivered the session
• Diagnosis: the ICD-10 code is current and explains why land-based exercise will not do
• Plan of care: signed, dated, and still inside its certification period

Each of these is a clean claim requirement. Catching one now costs far less than appealing it later. Five points, thirty seconds, one claim that pays first time.

97113 or 97110? What decides it

Neighboring therapy codes describe similar work in different settings. Picking the wrong one counts as miscoding, even when the intent is honest. Here is what separates 97113 from the codes it sits beside.

Before you bill a new combination, check it against the payer’s own edits. The AAPC Codify CPT lookup confirms a descriptor quickly. Current NCCI edit tables show which pairs a payer bundles.

How Pabau keeps 97113 claims clean

Aquatic therapy billing usually breaks in the handover. A therapist writes the note, and someone else builds the claim. The minutes or the diagnosis get retyped along the way. Time-based codes punish that, because one wrong unit repeats across every visit in the plan of care.

Practice management software like Pabau closes that handover. Pabau handles claims management without rekeying. The payer, the diagnosis, and the plan of care come straight from the patient record. Built-in ICD-10 and CPT lookup libraries keep the codes themselves current. Completeness checks then flag a required field left empty before the claim goes anywhere.

From there, claims go out electronically through Claim.MD, our US clearinghouse integration. It supports CMS-1500 and 837P formats for thousands of US payers. Remittance advice comes back into the same record, so denial reason codes sit next to the visit that caused them.

For an aquatic therapy practice, that adds up to four practical wins:

• Therapy note templates that capture the session elements 97113 requires
• Claim fields pre-filled from the visit record, so nothing gets retyped between note and claim
• ICD-10 and CPT lookup libraries that keep diagnosis and procedure codes current
• Electronic remittance advice processing, so denial reason codes are tracked in one place

Send therapy claims without retyping the note

Pabau builds each claim from the visit record and keeps ICD-10 and CPT libraries current. Claims go out electronically through our Claim.MD integration. See how it works for a PT or OT practice.

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Conclusion

Aquatic therapy is worth billing properly, and the practices that do it well treat 97113 as a documentation code first. Three pieces carry the claim: the clinical case for water, the minutes that count, and the matching provider modifier. Get those three right and the code stops being a problem.

The trade-off worth remembering is time. Every minute you spend tightening a note template buys back the hours an appeal would cost, several claims later. Start with the one thing your denials keep pointing at.

Want the note and the claim to stay in step without retyping? Book a demo and we will show you how Pabau handles therapy billing end to end.

Continue your research

Need to understand the broader revenue cycle for your therapy practice? Revenue cycle management fundamentals covers how claims move from scheduling through payment posting.

Billing across multiple rehabilitation code types? Superbill documentation guidance explains how to structure superbills for time-based therapy codes.

Seeing the same rejections every month? Denial management in healthcare sets out a workflow for tracking reason codes and fixing the cause.

New to the claim side of the practice? What medical billing involves walks through each step from encounter to payment.

Managing insurance credentialing for your PT practice? Getting credentialed with insurance companies walks through the payer enrollment process for therapy providers.

Frequently asked questions