A hydrotherapy pool is a heated pool specifically designed for therapeutic treatment and rehabilitation, kept warmer than a standard swimming pool to help relax muscles, reduce pain, and support movement. While a typical lap pool sits around 78°F to 82°F (25.5°C to 27.5°C), a hydrotherapy pool used for therapy and rehab is usually maintained between 91°F and 95°F (33°C to 35°C). These pools are found in hospitals, rehabilitation centers, physiotherapy clinics, and some fitness facilities, and they’re built with specialized features that make them fundamentally different from recreational pools.
How a Hydrotherapy Pool Works
Three properties of water do the heavy lifting in a hydrotherapy pool: buoyancy, hydrostatic pressure, and resistance.
Buoyancy is the upward force that counteracts gravity. When you’re immersed in water, your body weight is partially supported, which reduces stress on joints and makes movement easier. Someone who struggles to walk on land may be able to move freely in chest-deep water. This unloading effect also reduces pain, making it possible to exercise muscles and joints that would otherwise be too painful to work with.
Hydrostatic pressure is the gentle squeeze that water exerts on your body from all directions. The deeper you’re submerged, the greater the pressure. This pushes blood from your limbs toward your core, increasing blood flow to your heart, brain, and lungs. When the water level reaches your chest, this fluid-shifting effect is strong enough to increase the heart’s output while lowering the heart rate. The pressure also helps reduce swelling in the limbs, which is why hydrotherapy is popular for post-surgical recovery.
Resistance comes from water’s viscosity. Every movement you make in water meets more resistance than the same movement in air, which strengthens muscles without the need for weights or machines. You can also control the intensity simply by moving faster or slower.
Temperature Settings for Different Conditions
There’s no single “correct” temperature for a hydrotherapy pool. The ideal setting depends on who’s using it and what they’re doing. Therapy and rehab sessions typically use the warmest range, 91°F to 95°F (33°C to 35°C), because the heat relaxes muscles, increases blood flow, and eases stiffness. But warmer isn’t always better.
People with multiple sclerosis do better in cooler water, around 80°F to 84°F (26.5°C to 29°C), because higher temperatures can worsen neurological symptoms. Pregnant women also need cooler water in that same range to avoid overheating. For arthritis, the Arthritis Foundation recommends 84°F to 90°F (29°C to 31°C), warm enough to soothe joints but not so hot that it becomes uncomfortable during extended sessions. Fibromyalgia patients may benefit from a wider range, 86°F to 96°F (30°C to 35.5°C), depending on what feels best. Facilities that serve multiple populations often keep their pools around 83°F to 86°F (28°C to 30°C) as a compromise.
Conditions That Benefit From Hydrotherapy
Hydrotherapy pools are used to manage a wide range of conditions. Some of the most common include osteoarthritis, fibromyalgia, Parkinson’s disease, neuropathy, ankylosing spondylitis, multiple sclerosis, and cerebral palsy. The common thread is that these conditions involve pain, stiffness, reduced mobility, or muscle weakness, all of which respond well to the combination of warm water and low-impact movement.
For people with osteoarthritis, the buoyancy takes pressure off damaged joints while the warmth loosens stiff tissue, making it possible to build strength and range of motion that would be difficult to achieve in a gym. For neurological conditions like Parkinson’s disease and cerebral palsy, the water provides a safer environment to practice balance and coordination because the risk of falling is essentially eliminated. The water’s resistance also slows movements down, giving the brain more time to coordinate motor patterns.
Specialized Equipment and Design
Hydrotherapy pools look different from recreational pools because they’re built around accessibility and clinical function. Most feature hoisting equipment to lower people with limited mobility into the water, along with wide stairs with handrails for those who can walk but need extra support. The pool deck and entry points are designed to accommodate wheelchairs and stretchers, with a clear path from changing rooms through showers to the pool edge.
One of the most distinctive features is a movable floor. This is a platform that can be raised or lowered to change the water depth for each patient and exercise. A therapist might set the floor so the water reaches a patient’s waist for walking exercises, then lower it for deeper immersion during stretching. When raised to deck level, the movable floor also makes transfers into and out of the pool much easier for people who can’t use stairs.
Many hydrotherapy pools also include underwater treadmills, which allow patients to practice walking with reduced body weight. When a treadmill is built into the movable floor, the therapist can adjust both the walking speed and the water depth, fine-tuning exactly how much of the patient’s weight their legs need to support. Some pools have underwater observation windows and cameras so therapists can analyze gait patterns and joint mechanics from outside the water.
Common Therapeutic Techniques
Sessions in a hydrotherapy pool range from simple walking and stretching to specialized methods. Standard aquatic therapy involves a therapist guiding you through exercises tailored to your condition: walking patterns, resistance movements, balance drills, and range-of-motion work. The therapist is typically in the water with you or standing poolside, depending on how much hands-on support you need.
One specialized approach is Watsu, a portmanteau of “water” and “shiatsu.” During a Watsu session, a therapist holds and cradles you in chest-deep water kept around 95°F (35°C) while performing gentle stretches, joint mobilization, and massage-like techniques. You float while the therapist guides your body through slow, rhythmic movements. It combines elements of physical therapy with deep relaxation, and it’s used for both rehabilitation and stress reduction. Because the therapist adapts every movement to what your body needs in the moment, no two sessions look exactly alike.
Water Quality and Safety Standards
Because hydrotherapy pools run warmer than standard pools, they require more rigorous maintenance. Warm water creates a more hospitable environment for bacteria, so disinfectant levels need to be higher and checked more frequently. Public therapeutic pools maintain free chlorine at a minimum of 3 parts per million (compared to lower levels in cooler pools), with pH kept between 7.0 and 7.8. Disinfectant and pH levels are tested at least twice daily, and hourly during heavy use.
The water is drained and replaced on a weekly to monthly basis depending on how heavily the pool is used, and filtration systems run continuously. A biocidal shock treatment is applied daily to weekly. Water temperature in any therapeutic pool should never exceed 104°F (40°C), which is the safety ceiling to prevent overheating and cardiovascular stress.
Who Supervises Sessions
Hydrotherapy sessions in a clinical setting are typically led by licensed physical therapists, occupational therapists, or athletic trainers who have additional training in aquatic therapy. An aquatic therapy certification doesn’t replace an existing clinical license. It adds specialized knowledge about water-based treatment to a therapist’s existing qualifications, covering topics like how to adapt exercises for the water environment, how to use pool equipment safely, and how to manage emergencies. Facilities also coordinate with lifeguard personnel and maintain emergency action plans specific to the pool environment.
Recreational hydrotherapy, like using a warm pool at a gym or wellness center for general relaxation and low-impact exercise, doesn’t require a therapist. But if you’re using a hydrotherapy pool to manage a specific medical condition, working with a qualified professional ensures the water temperature, depth, and exercises match what your body actually needs.