A leak detection investigation.

I knew my day was going sideways when it was going to be necessary to change into a bathing suit and get wet in the customer’s master bath in order to find out what was causing a leak into the basement. Did I mention the owner was an attractive divorcee who had recently purchased the home? No way was I going to continue the forensic investigation in a bathing suit by myself, so I recruited one of the other employees to join me on site. 

This was no ordinary master bathroom — it was palatial in size with a wide double vanity, toilet and bidet as well as a makeup vanity and lots of open floor space. The spa area was a walk-down curved stairway that opened up to a ceramic tiled basin that was an 8 feet long by 5 feet wide waterpark! On the far wall, there was a Kohler high-flow shower faucet with a sunflower showerhead and multiple body jets. On the common wall to the master bath, there were two Kohler high-flow shower faucets with one connected to a massive rain-head in the ceiling and the other shower faucet with a hand-held multifunction shower wand and a high-flow showerhead. The waterpark’s crowning feature was a Kohler 80 gpm, 10-jet tower! 

In order to use the 10-jet tower, it was necessary to fill the “pool” area with more than 200-gallons of water to cover the suction intake for the 80 gpm pump. Now you know why I needed the bathing suit! Before I reveal the source of the leak, and it was more of a river than a typical leak, let’s review what oddities were uncovered in this investigation. 


One of the customer’s complaints was the lack of water pressure whenever she attempted to use any of the spa area high-flow shower valves. I noticed the adjustment screw was turned all the way down on the 1-inch PRV for higher pressure. The first step was measuring static and operating pressure, which revealed 80 psi static, but just 12 psi with any spa shower faucet open. A call to the local water company revealed street pressure was more than 110 psi, so the PRV was needed to protect the plumbing from excessive pressure. The inlet screen was clean with hardly any debris. 

The fact that the adjustment screw was turned down to its maximum pressure setting indicated the previous owner had been aware of the low operating pressure issues. Using a bucket and my refrigerant digital scale, the maximum operating flow was just 2.2 gpm. Timed flow, total weight less the empty bucket’s weight and the net water-weight divided by 8.34 to obtain gallons. 

After installing a new 1-inch PRV with its pressure adjustment screw turned halfway down, I had 80 psi static and with all three Kohler high-flow shower valves open in the spa area, operating pressure was a solid 68 psi. 

Tankless water heater oddities

Three 82% efficiency tankless water heaters were in the basement with two of them working in tandem to serve the master bath and its spa area. The third tankless served the kitchen, laundry, half-bath and guest bathroom. All three were not installed in compliance with the manufacturer’s instructions. The new homeowner provided a copy of the certified home inspector’s report, which included no mention of any issues with the tankless water heaters! No backdraft damper and galvanized (stainless steel required) flue piping begged the question nagging at my brain, and a call to the local supply house that carried that brand revealed the heat exchangers had frozen and split on several occasions! 

This had been the developer/builder’s home, and the manufacturer had donated the tankless water heaters, which probably explained why each one was a different Btu/h size. You’d at least expect the twinned tankless water heaters parallel piped to be equal in output, but they were not, and flow had been “balanced” by partially closing the outlet ball valve on the larger Btu/h model. The distribution piping was a hodgepodge of PVC and CPVC plastic. Given the 80 psi static pressure and fluctuation in outlet water temperatures that ranged between 120° F and 140° F, depending on gpm flow and opening/closing faucets, the 1-inch PVC schedule-40 had a maximum pressure limit of 99 psi.

In order to turn on the tankless water heaters for the master bath lavatory faucets, the flow restrictors had been removed from their aerators. 

A large potable water expansion tank had been installed under the master bath spa area, which no doubt had been an attempt to provide a buffer for water pressure fluctuations. However, at the 15 gpm flow rate for each of the Kohler high-volume shower valves, it would only be a minute or two before the expansion tank would become exhausted. 

The underside of the recessed framing supporting the spa had obviously suffered years of water leaks, especially on the end and side opposite the 10-jet water-tower, so it was time to dive into the deep end of the spa pool! 

As you would expect, the first leak-check after running all three shower valves, body jets and shower heads with no leaks into the basement, was pouring water over the shower valve plates and body jet wall escutcheons. It’s the logical progression when trying to find a leak from a bathing module, and still no leaks appeared. The next logical step, as you would with any ceramic tile shower pan, is to plug the drain and fill the base. That was necessary anyway in order to test the 10-jet 80 gpm shower-tower. 

Water temperature within the recessed floor basin quickly lost its heat to the surrounding masonry products and even more rapidly once the recirculating system was activated. Although we were receiving water that varied from 110° to 120° at the various shower heads/jets, the temperature within the 211 gallons had dropped to 87° by the time we could attain proper depth. That dropped off to 83° following five minutes of shower-tower runtime. Kohler’s catalog lists the ten-jet system as including an integral heater. However no heater could be located during our inspection.

Leak revealed

Immediately upon activating the shower-tower’s pump, the 10 streams of water traversed the distance across the spa area, directly impacting the opposite wall and one of the jet streams of water hit the bull’s-eye on the Kohler shower faucet body. Water immediately began pouring out of the basement framing for the spa area and spread horizontally to appear in a wide area. 

Shower faucet wall plates are quite good at shedding water, but are certainly not designed to handle the direct head-on impact of a very forceful horizontal stream of water! The pump and piping for the shower-tower were not accessible, as no access panels had been provided by the builder-owner. 

Resolution (or not)

A detailed four-page letter was delivered to the owner detailing all I had discovered with a breakdown of costs for each issue that needed to be resolved. I went over each item with her in layman’s terms and she understood why the repairs were needed. 

Let’s just say she was not a happy camper and told me she was going to go after the builder/owner for not disclosing the many defects. That was the last I ever heard from her, so I had no idea if any of the resolutions had been done. Perhaps she shopped my pricing with other mechanical contractors and got a lower price. 

Two years later, I fielded a phone call from a man who told me he was having problems with his shower leaking down into the basement. “You may want to come over here to see this bathing area because it has multiple showers and a 10-jet wall-mounted tower.” 

You guessed it: same home, now a third owner. Had the divorcee revealed the defects and shared my original 4-page letter/proposal? No! After removing any references to her, I did provide him with a letter detailing the prior findings and suggested resolutions. He told me he simply wouldn’t use the 10-jet tower. 

This article is also available at: https://www.pmmag.com/articles/103513-dave-yates-immersed-in-your-job