Unfortunately, the hydronics industry lacks a standardized testing procedure. These tests are routinely performed by contractors who are not qualified, experienced, or properly licensed to perform this work.

This ends up in invalid test results and homes being sold with a leaking system. How can we remedy this problem?

The Uniform Mechanical Code defines the requirements for testing radiant panel heat. Section 1208.1 Hydrostatic Test states, “Approved piping or tubing installed as a portion of a radiant panel system that will be embedded in the walls, floors, or ceilings of a building it is designed to heat shall be tested for leaks by the hydrostatic test method, by applying at least 100 psi of water pressure or one and one-half times the operating pressure, whichever is greater.”

Note that the code requires a hydrostatic (water and not air) test with a minimum test pressure of 100 psi. These requirements are very specific and apply to all radiant panel systems.

Since the normal operating pressure of an Eichler radiant heat system is 10 to 20 psi, 1.5 times this would be 15 to 30 psi. This is less than 100 psi, so the proper code testing pressure for the system is a minimum of 100 psi.

There are no exceptions to these requirements for the materials used in the distribution system. The tubing could be copper, steel, plastic, polybutylene, polyethylene, or rubber.

These requirements apply to the distribution tubing only and not the boiler safety and support equipment. Another code, the National Boiler Code, applies to the boiler and its equipment.

Anderson Hot Water Heating agrees that any copper, plastic, polybutylene, polyethylene, or rubber tubing can be safely tested to 100 psi regardless of its age. The only exception, learned through many years of field examination and experience, is any steel tube system should not be tested at this pressure. (Reasons for this will be explained later.)

Min/max requirements

The National Boiler Code defines the minimum and maximum requirements for testing the boiler and support equipment. This code applies to the boiler equipment of the radiant panel system.

All boiler manufacturers support this code and certify their boiler per these procedures. There are no exceptions, whether the boiler is installed in residential or commercial property. These equipment codes apply in both instances.

Because a hydronic radiant panel system uses a low-pressure boiler as the heating source, the concealed radiant panel is defined as being part of the “support equipment.”

The code states, “The minimum system testing pressure is a pressure equal to 1.5 times the psi rating of the pressure relief valve; the maximum test pressure is a pressure equal to 90% of the boiler test pressure, as set by the manufacturer.”

What does all this mean? As an example, the A.O. Smith HW Series boiler commonly found in many Eichler and custom homes, is pressure tested to 160 psi by the manufacturer. This means a proper pressure test of the radiant panel tube with this boiler installed would be a minimum of 45 psi (if the boiler has a 30-psi pressure relief valve) and a maximum of 144 psi (as defined by the manufacturer’s rating).

As another example, the Teledyne Laars JVC Series boiler has a maximum manufacturer’s test pressure of only 30 psi. The pressure relief valve commonly installed is 30 psi. This means the minimum and maximum test pressure would be 45 psi (as defined by the pressure relief valve).

The test pressure and working pressure of a boiler can be different. The manufacturer’s test pressure is always as a minimum at least 1.5 times the working pressure of the boiler. These pressures are easily identified and stamped on the boiler. This code disregards the type of radiant panel tubing embedded in the concrete.

Which code?

The most important question a hydronics contractor should ask is: Should we pressure test the hydronic radiant panel in accordance with the Uniform Mechanical Code, the National Boiler Code, both, or neither?

Before we can answer this question, we must consider whether any testing can cause damage to the radiant panel.

For the hydronic contractor, the type of tubing in the radiant panel should define the test procedure and pressure regardless of the system age. The burst pressure of the type “L” copper used in the radiant panel exceeds 1,000 psi. Therefore, a pressure test of 100 psi or less certainly will not cause a copper tube to burst.

Experience indicates that a properly administered pressure test of 45 to 100 psi meets the requirements of both codes and, when monitored for 45 min, will significantly detect any radiant panel leaks. The closer the test pressure is to 100 psi, the better the test will indicate any leaks.

Test pressures of less than 45 psi will not, in many cases, detect small leaks within the radiant panel. The only purpose of the hydronic pressure test is to determine if there are any leaks, large or small, in the radiant panel. The concern of causing a leak because of pressure testing is irrelevant. Since the leaks in any copper tube system are the result of slab stress which may split the tube, a test performed by the procedures to follow will not cause a tube to burst. It is only logical to conclude that a tube was leaking prior to the test if the results indicate there is a leak (or leaks) in the panel system.

There is no method to determine if a pressure test caused a tube to burst. In the unlikely event it did, in order to meet the testing requirements of the codes, the tube should be repaired.

Leaks from degradation

Forty years of experience in working on the Eichler and custom hydronic homes has taught us leaks in steel tube radiant panels are caused by electrolysis. This results from the improper installation of the tubing in the concrete, and steel materials which oxidize, corrode, and rust.

Electrolysis is the chemical degradation of the tube catalyzed by one of the following conditions:

  • Electrical grounding of the house outlets;

  • TV and telephone cables into the radiant panel;

  • The introduction of new water into the system from leaks;

  • Poor installation procedures, such as leaving the tubing on the grade rather than raising it into the concrete; and

  • The contact of exposed tubing with contaminated soils.

    These conditions will result in the formation of acids that cannot be flushed from the system and eventually corrode through the tube.

    At the time of the concrete pour, the plastic coating on the steel tubing designed specifically for the Eichler home could be inadvertently chipped off by shovel edges of inexperienced workers moving the concrete.

    If the steel tube was not raised to a proper level within the concrete and left to lay on the grade (which was a common practice), corrosion and rusting of the steel tube would occur at the chipped point.

    Because of the nature of steel tube Eichler homes, it is extremely important that only experienced and qualified personnel perform the pressure test.

    Overpressurization of any steel radiant panel that has been subjected to the above conditions may cause the tubing to leak. Many steel systems that have not been subjected to attack from outside environmental factors are leak-free.

    Any steel tube radiant panel should be hydrostatically tested for 2 hrs at the operating pressure noted on the system gauge, or 10 psi.

    The simple facts are, most Eichler homes with steel tubing will not pass a code-approved test because testing them at the pressures defined by the code could cause severe damage to the tubing.

    The difference between the copper and steel tube Eichler and custom home is like night and day.

    Recommended testing

    Anderson recommends the following test procedures for hydronic contractors to perform a proper and valid test of any radiant panel system.

    1. The system shall be at ambient temperature for a minimum of 24 hrs. This requires the gas supply to be turned off to the boiler for 24 hrs prior to performing the test.

    2. The air expansion tank shall be isolated or removed from the system prior to the test.

    3. The pressure relief valve will be isolated or removed from the system prior to the test. It is not sufficient to plug or cap this valve. It must be removed from the test side of the system. Cap or plug the point of removal.

    4. Do not flush the panel system prior to the test. Test copper tube systems at 45 to 100 psi for 45 min. Test steel tube systems for 2 hrs at the pressure noted on the system gauge or 10 psi.

    5. Testing may be accomplished with the boiler installed in the system if the above conditions are met. The best test of the radiant panel is to isolate the tubing from the boiler.

    This is not always practical. Either test method is acceptable. When testing the radiant panel and boiler together, the test will be accomplished per the National Boiler Code. When testing the radiant panel only, the test will be performed per the Uniform Mechanical Code.

    6. The test must be performed by the hydrostatic method. This means using water to pressurize the radiant panel.

    The introduction of any gas (i.e., helium, nitrogen, or oxygen) to pressurize the system is totally unacceptable, improper, and will result in invalid test results.

    7. Verification of the system pressure prior to, during, and after the test is extremely important to all concerned parties. Ensure that a separate and distinct pressure gauge with minimum degradations of 1 psi or less is used for the test.

    Under no circumstances should the system gauge be used or substituted for the test instrument.

    8. If a drop in pressure is noted, repressurize the system with water only and perform the test a minimum of three times. This will verify the test results by ensuring they have not been affected by air compression, temperature changes in ambient conditions, or boiler cool down.

    The owner of a radiantly heated home can often be fooled into believing the heating system is operating properly even if leaks are present.

    Remember, 90% of all radiant panel leaks never surface into the home, nor provide a “wet spot” at the point of the leak. The leakage is generally directed downward and into the grade below the concrete.

    Only through proper maintenance and system monitoring can the homeowner be ensured of a safe, efficient, and reliable radiant system.

    End the confusion

    It seems that whenever two different companies become involved in the pressure test and inspection of Eichler and custom homes, the testing results can differ dramatically. This confuses the homeowner, buyer, seller, agent, and anyone else involved with the sale of the home.

    Confusion results from different philosophies, non-standardized testing procedures, and inexperienced hydronic contractors. Anderson Hot Water Heating feels the only proper testing method is to follow the guidelines set forth by the Uniform Mechanical Code, National Boiler Code, common sense, and our suggested procedures.

    There are too many homes being sold containing radiant panel leaks because an improper testing procedure failed to identify the leaking condition.

    To elevate our industry’s reputation to the level we deserve, Anderson hopes other hydronic contractors will follow our recommendations and standardize their testing procedures.