Pressure Testing, Leaks, and System Maintenance Questions

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How often should I perform a pressure test of the concealed tubing system?

The following conditions warrant a pressure test:
  • Whenever the home is sold or every 2-3 years
  • Whenever a service person suspects a leak in the concealed radiant panel system
  • Whenever you remodel the property or replace any floor coverings
  • Whenever any slab penetration is required, for example, drilling for termites

Can a pressure test cause leaks in the concealed tubing system?

It depends on the tubing material and the condition it is in. Some materials are rated for higher pressures than others and some hold up better over time than others. A qualified service person should be able to determine the proper pressure testing procedure after inspecting the individual system to identify what precautions, if any, should be exercised when accomplishing the test. There are Universal Plumbing and Mechanical Codes which define the pressures to be used for testing concealed piping systems. It is always advised where the condition of the piping is not a concern to pressure test the tubing system at least at city water pressure. The increased pressure for the test allows the serviceperson to receive more accurate and sensitive results within a shorter period of time. Any air in the piping system is compressed and minor losses can be detected easier. A routine service call usually does not lend the appropriate amount of time to determine accurate results at system operating pressures. For example, a “closed-loop” copper radiant panel system does not deteriorate and can be tested at city pressure at any time. Copper tube systems are rated for pressures greater than 500 psi so performing a test at 60 psi or less presents no potential danger. On the other hand, if the tubing system is composed of steel where the question of deterioration may exist, we always recommend testing the radiant panel at the system operating pressure or 10 psi , whichever is greater, for a longer period of time. A standard city water pressure test should be performed for at least 45 minutes and a system operating pressure test for an hour and a half. Plastic and rubber tubing systems also have reduced pressure limits from the start. Unlike the steel and copper systems which originally had a 500 psi bursting strength, the plastic and rubber tubings are rated at a maximum of 100 psi. We recommend never testing these systems at over twice the system operating pressure or 20-30 psi because of the tubing, unions and joints which may unknowingly be weak and leak. The National Boiler Code states the system should be tested at 1-1/2 times the pressure relief valve capacity or 90% of the maximum rated capacity of the boiler which ever is more. The Uniform Mechanical Code requires all radiant panel systems regardless of material type to be tested at 100 psi prior to pouring the concrete. In their perspective of safety, a tubing system regardless of it age should be able to conform to the original pressure testing standards or it is not safe to be used anyway. Our recommendation for reduced pressure testing standards for plastic, rubber and steel systems is a reasonable compromise for promoting a systems longevity should intermediate stages of deterioration exist. See our information page titled “The truth about pressure testing radiant panel systems” which has been nationally publicized.

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I have heard of problems concerning leaks in radiant heating systems. Why do they occur and how can I be sure there will be no leaks in my system?

Leaks have occasionally developed in radiant panel systems due to different reasons depending on the material type used. Review the following problems seen with each material type.
  • Steel tubing systems: Problems with leakage mostly caused by external environmental factors combined with poor installations techniques. The steel piping originally had a plastic protective coating around the tube which was supposed to guard against rusting and corrosion. The plastic coating either wore off or was chipped off during installation which made the tubing susceptible to attack from external moisture. Improperly installed, the tubing systems were often pushed to the bottom of concrete slab which positioned the radiant panel for attack from outside ground moisture. The result was external rusting and eventual leaks. Since the systems were designed “closed-loop”, no new oxygen or minerals entered the tubing to promote internal corrosion. Steel systems properly installed within the concrete slab and not subjected to moisture through large cracks can last the life of the structure. Some systems 50-60 years old are still running perfectly today.

  • Plastic tubing systems – Leakage has developed for several reasons including tubing becoming hardened and brittle over time. Hairline fractures have occurred in tubing circuits which travel distances and are non-repairable to code. Leaks have occurred at the unions and joints required for the above ground connections to manifolds and boiler equipment. Expansion and contraction caused by system temperature differences and the molecular changes in the plastic from heat have sometimes allowed leaks to develop at the unions, crimped fittings, and compression fittings. Boiler equipment failures and increased system operating pressures resulting from support equipment failures have lead to leakage problems as well. Plastic tubing systems are rated at a 60-100 psi maximum working pressure. Expansion tank, pressure reducing valve, and pressure relief valve failures, although rare, can allow the pressure to increase promoting stress on the piping material which may already be weakened. Increased system temperatures have affected some plastic tubing systems. Oxygen permeability for the majority of plastic tubings has led to early equipment failures.

  • Rubber tubing systems – Leaks have developed from the deterioration of the rubber material due to heat exposure, concrete exposure and water content. Material has low pressure ratings which has experienced similar problems seen in some plastic systems due to increased system pressures. Again, connections at manifolds have leaked regularly. Oxygen permeability allows outside air to filter into a closed system and cause premature equipment failure.

  • Copper tubing systems – Leaks have sometimes occurred because of stress related issues due to slab movement and earth shifting in monolithic(single slab) concrete pours. In most cases, poorly re-enforced slabs and unsettled ground have allowed repetitive slab movement at cracks in the slabs. The bound tube on both sides of the crack can be stressed and eventually split from the pulling. No leakage has been seen in two-slab pours and in slab-on-raised wood sub-floor construction. Single slab pours with proper rebar content and laid on solid ground have rarely experienced the problem. The soldered/welded joint construction, pressure ratings, temperature rating, corrosion resistance, and non-permeability of copper tubing has not exposed itself to the problems of the other tubings.

To ensure leaks will not occur in your tubing system, the proper material must be chosen for the distribution panel. We suggest an all Type “L” copper radiant panel that is installed either on a wood sub-floor with a light-weight concrete or in a slab-on-grade with a two-slab pour. Both environments are completely stress-free and will ensure a trouble-free system. Whether or not copper, plastic, or rubber tubings are used for the radiant panel, it is always smart to have a pressure test on the tubing system prior to, during, and after the pouring of concrete. Examination of all individual system joints is recommended as well. This will ensure the radiant panel is leak-free throughout the entire construction process. If a tube is punctured by an unsuspecting individual during or after the concrete pour, they will immediately know to notify the heating contractor so the problem can be fixed.
Typically not, but the type of tubing material will affect your ability to repair the system. Your radiant panel system is carefully tested before being covered with concrete and the chance of a leak developing in the tubing for new construction is very remote. However, should some accident occur, modern instruments which detect helium injected into the tubing can pin-point the trouble in a very short time. If the radiant panel is composed of all copper then the repair is easy. A small opening in the floor is necessary to access and perform the repair. Copper repairs can be sliver-brazed to meet code and recovered with concrete. Any required repairs on plastic or rubber system can not be repaired to code if recovered with concrete. A knockout plate must be installed in the floor to provide future service access to the repair. Depending on the nature of the leak and the amount of tubing requiring replacement, repairs may or may not be feasible. For repairable sections of piping, union, clamp, and compression fittings are generally used for the repairs. Steel systems can be soldered if the piping is not pitted or deteriorated. If the steel tubing is in bad shape then no proper repair can be made and the system must be replaced. In some cases on-site evaluation is required to determine the extent of the repairs needed. Most of the repairs on older homes are covered by homeowners insurance.

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Should I have a service person check the operational condition of my boiler each heating season?

Yes, as recommended by the equipment manufacturers. It is especially recommended for systems that are 30 years and older. It is true that a properly running radiant heating system can run for years without required service; however, yearly inspections of the system by a qualified Hydronics Contractor will ensure your system will continue to operate properly, efficiently, and safely. If you live in our area, follow the recommendations outlined on the "Operational Checklist for Copper Tube Radiant Heat Systems" provided by ANDERSON RADIANT HEATING. The homeowner can participate in monitoring the condition of their system between the inspections performed by a qualified service person. Call a service person anytime you suspect a malfunction of the radiant heating system.

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520 East McGlincy Lane, Suite 16
Campbell, CA  95008
Phone: (408) 378-3868
Fax: (408) 559-0818

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