By Roland Reisley, original client and current homeowner

Taken from the Building Conservancy’s Bulletin, summer 2002

After 1936 Frank Lloyd Wright specified radiant heating in most of his designs. Hot water circulated in pipes buried under the concrete floor enables a particularly comfortable winter environment marked by lower air temperature, higher humidity, less dust and the pleasantly warm floors. Unfortunately, over 40 to 60 years, some of these systems

have developed leaks that, unlike exposed radiators, may be difficult to locate and repair. The perceived difficulty and the shibboleth, “don’t bother, one leak will soon be followed by more” has led to premature abandonment of some radiant systems. Replacement, too, is difficult, expensive and often architecturally devastating. Building owners should note that, in many cases, leaks can be located and repaired and that many “plumbing and heating” contractors do not have the knowledge or patience for these tasks.

Maintenance of the aging radiant systems is the most serious concern that is common to so many Wright buildings. This ongoing issue was discussed in 1998 Bulletins, Volume 7, Nos. 2, 3 [the Morosco articles]. Breaking into and restoring concrete floors is scary, but not very difficult or expensive. The hard part is locating a hidden leak. With luck, it might be an easily found wet or hot spot. Or it may be audible. The sound of escaping water or air can be detected in many ways from simply the unaided ear to stethoscopes to sophisticated ultrasound receivers. (Commercial/industrial leak finders use high pressure to hear leaks. This method however may be destructive.) Even so, locating the leak will likely require patience and some skill.

In the Reisley House (1951, 1956) the radiant system, Rayduct (steel) pipes (originally installed in 1951) has not leaked. The 1956 addition however leaked in 1988 and again in 2000. Both were successfully repaired. In 1988, after months on my hands and knees with a stethoscope and only vaguely identifying a warm area, I gave in, increased the water pressure from the normal 15 pounds to 45 pounds, which confirmed the location.

In the late 1990s, occasional slow leaking was stopped by infusions of Boiler Liquid* (stopleak), but it soon became apparent that it was time to find the leak. One area of about 200 square feet seemed warmer than the rest, but nothing could be seen or heard. A knowledgeable plumber (i) suggested the following system: attach an air compressor limited to 20 psi then fill the system alternately with air and water. Brief intervals of turbulence, noisier than a steady flow of air or water, should occur at the leak. After some repeated cycles, it was possible to confirm the sound in an area of four or five square feet. The floor in this case was terrazzo, much more difficult to repair than concrete. Hoping to locate the leak more precisely, a valuable new tool was discovered.

Stethoscopes, the most commonly used leak detectors, frequently are not effective. They are intended for low-pitched sounds, heartbeats, etc.. Leaking water quietly makes many sounds that are ultrasonic, that is, beyond the range of human hearing. Sensitive electronic instruments however can detect them. UE Systems*, Inc. (ii) manufactures a variety of ultrasound detectors.[] Their Marketing VP, Alan Bandes, agreed to demonstrate the equipment in our efforts to locate the leak exactly. To illustrate its sensitivity, the blink of an eye at a distance of 10 feet was received as a loud click. ,

Joining our plumber expert Mark, Alan moved the “Ultraprobe” around the suspect area [Figure 1], stopping at the loudest point. Mark “attacked” at that point [Figure 2] and soon uncovered the leak. It was in a bend, perhaps a weakened stress point. [Figure 3] The pipe was replaced, surrounded with gravel and covered with concrete to an inch below the surface – leaving room to replace the terrazzo. [Figure 4] Correctly locating the leak limited damage of the floor to a single module– and the heating system is working perfectly. Ultrasonic detection is probably the most effective and practical method for locating hidden leaks, but it should not be considered a “magic wand.” The instruments are now in the hands of a number of franchised practitioners. Nevertheless, diagnostic “art” and patience will almost always be key to success.

  1. Mark Roberto, of Richard Bell Plumbing & Heating, Millwood, NY
  2. UE Systems, Inc. 14 Hayes Street., Elmsford, NY 10523

Fig. 1 Searching the suspect area

Fig. 2 Breaking in

Fig. 3 The bend that leaked (external corrosion)

Fig. 4 Accurate location limited damage to a single module.

Reisley House Revisited 2022

By Roland Reisley

For a few weeks we were puzzled by an intermittent scratching sound that we thought might be caused by an animal inside the roof. I made an appointment for a wildlife person to explore. My grandchildren were visiting and said the sound was coming from the floor—near a large stone in the fireplace hearth. They were right. It was intermittent hissing from a pipe under the stone. About 20 years ago I repaired a leak there.

The expert plumber who helped me with radiant problems had retired but offered to return. There was a leak about a foot away from the original one and another in an adjacent pipe. The pipes were now quite fragile but he was able to repair. He knew a good mason who was able to cut and then renew the concrete floor. Here are some photos. It took three days and the heat is now working perfectly.

About 20 years ago I wrote an article for the Bulletin on finding and fixing leaks. The ideas should be shared with new owners of houses with radiant concrete floors. Inexperienced plumbers urge abandoning them too soon. Finding and fixing leaks is easier and much less costly than a new system–which, sadly, will ultimately be needed.

Unfortunately this topic will continue engage us.

Intermittent hissing at the Reisley house proved to be several small leaks in the original radiant heating system, which were repaired, and the floors fixed, over the course of 3 days.

* Please Note: The provision of this information or mention of a specific product or products does not constitute endorsement, recommendation, preference or approval by the Conservancy. It provided only as a record of activities and as a starting point for further research by other building stewards.


Radiant Heating 101 - Introduction Page

Posted April 3, 2023