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Mechanical mayhem: defects hidden in plain sight

Sept. 1, 2010
What leaps off the page from a professional mechanical contractor’s perspective will be virtually invisible to others: hiding in plain sight

The owners paid a cool $1.5 million to the bank, a bargain-basement sale price for their 16,000-sq.ft. McMansion with its granite countertops and a grand entrance large enough I swear there was an echo! (The builder had gone belly-up and the subcontractors had not been paid.) I wasn't there to admire the tricked-out kitchen or the massive flat-screens with surround sound that the builder tossed in as an incentive during his last-ditch effort to survive the weak economy. You know why I was there: problems with the mechanical systems.

Their concerns were running out of hot water; low pressure if anyone else uses plumbing while someone is showering; mold (yikes!); temperature imbalances in various rooms; and noise when any of the six HVAC systems were on.

A six-bedroom home with six full baths: well, in reality we could classify the massive master bathroom as two full baths at more than 400-sq.ft. with separate his-and-her water closets (hers with the bidet); twin lavatory bowls separated by a long stretch of granite; platform-elevated whirlpool tub surrounded by a wall of glass to enjoy the view; and walk-in, glass-encased dual showers with high-volume sunflower showerheads and enough body jets to fly you off to a blissful paradise — if only the mechanicals supported the end-use potential.

"We use the showers for no more than a few minutes and then run out of hot water," said the owners. "The pressure is OK with just one shower faucet on, but as soon as you turn on the second valve, or water is being used in any other bathroom, the pressure is lousy."

Off to the mechanical room (more like off to find the scattered-about mechanicals). A ¾-in. water service serving this home! Next to it was the incoming gas line that immediately met up with the corrugated stainless steel tubing (CSST) manifold. A helter-skelter tangled mass of CSST lines disappeared over the nearby wall and beyond that was a large expanse of plastered ceilings. One of the six 92% efficiency single-speed furnaces was shoehorned into this closet-like space while its 13-SEER air conditioning partner was more than 75 feet away. I found out from the owners that this home was completed in 2008 as a "spec-home."

The water heater, as you might have guessed, was located as far away from the master bathroom as possible. It was a 50-gal. gas-fired indirect-vent (uses room air for combustion, but vents by-products of combustion via a PVC side-wall exhaust) model with ¾-in. water inlet/outlet. All of the home's hot water branch lines connected between this tank and the last-on-the-line riser to that far-away master bathroom — ensuring volume and pressure would be reduced along the hot-water highway.

"Give us a price on a tankless model … from what we've read, that will solve the problems," said the homeowners.

Not so fast! Although I could use the existing side-wall vent with a high-efficiency model, we needed to find a route for the new gas line. Using the existing line was not an option since it was only ¾-in. diameter, which was adequate for the existing 38,000-BTU load, but it couldn't support enough gas-flow to meet a 240,000 BTU gas flow.

"Can’t you install a smaller tankless model — one that will be able to use the existing line?" asked the homeowners.

Let's revisit the mechanical space where the gas line enters the home: I was hoping to find a way to back-feed the master bath via another hot water line, isolate that portion of the DHW distribution and let the kids have the 50-gal. water heater. It would have been easy to tie into the gas line ahead of the manifold and the short run to the gas meter would have supported the total connected load. That way it might be possible to resolve the running out of DHW and alleviate, to a large degree, the pressure woes by adding a variable-speed booster pump. However, the lone hot water line exposed was ½-in. Lots of plastered ceilings separated us from the lines serving the master bath.

The mechanical-mayhem investigation tour lasted for hours with one botched mess following another. The homeowners wanted to know why the home inspector had missed all the now-glaring defects. The problems weren't obvious defects unless you're fully trained in plumbing and HVAC issues. What leaps off the page from a professional mechanical contractor's perspective will be virtually invisible to others: hiding in plain sight. While it's not rocket science, it is applied science, and common-sense alone should have raised red flags regarding the use of an obviously undersized water heater. For example, if you don't have sufficient capacity to fill your whirlpool, you know there is a problem, which the homeowners discovered the first time they wanted to use the whirlpool.

Recommended cure
I recommended the following cure for this home's DHW issues:

  • Add up the peak demand load (PDL) in GPM and its duration to determine if a tank-style model of sufficient volume can be installed and supported by the existing gas line. No change in the pressure woes.

If that didn't work I recommended:

  • Remove plastered ceiling as needed to access the master bathroom water lines and install isolation valves (if that wouldn't create long dead-legs) or cut out the runs between the risers and the remainder of the existing hot/cold lines. Run new hot/cold water lines to the closet-like mechanical space where a new variable-speed booster pump (serving the whole home) would ensure some measure of relief regarding the loss of pressure when the dual shower was in play. Last, but not least, install a direct-vent (both fresh-air and exhaust are vented to the exterior) high-efficiency tankless water heater.

"No way we're spending that kind of money … we'll get someone else," the homeowners said after I gave them my recommendation.

Who knows — maybe one of the next plumbers they contact will see a novel solution I missed at a price-level they can afford.

Dave Yates owns F.W. Behler, a contracting company in York, Pa. He can be reached by phone at 717/843-4920 or by e-mail at [email protected].

All Dave Yates material in print and on Contractor's Web site is protected by Copyright 2010. Any reuse of this material (print or electronic) must first have the expressed written permission of Dave Yates and Contractor magazine. Please contact via email at: [email protected].

About the Author

Dave Yates

Dave Yates material in print and on Contractor’s Website is protected by Copyright 2017. Any reuse of this material (print or electronic) must first have the expressed written permission of Dave Yates and Contractor magazine.

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