Walking into a worst-case mechanical system

Twin 3-in. PVC schedule 40 combustion exhaust and intake lines greeted me as I descended the basement steps Condensate is moderately acidic and had eaten away the surface of the floor An indirect-vent (exhaust only) gas water heater with a 20-ft. long horizontal 3-in. PVC schedule 40 had just one loop of plastic hangar strapping for support In addition to the PVC joints that were not glued together, the other joints had been glued together using CPVC cement and no primer It’s a miracle the piping had never separated to spew CO into their home 90-degree elbows had been installed turned to vertical with two-foot extensions The top of the furnace has been damaged from water escaping the cased A/C (air-conditioning) coil It’s stunning to come across work like this

Work for any lawyers? Do so with eyes wide open! I stepped into a potential minefield recently when a local lawyer asked me to check his HVAC zoning system to see if it could be put back in service. They had their HVAC equipment replaced a few years earlier and the installer had disabled their zone damper system.

“While you’re there, do me a favor and give the mechanical systems an once-over and let me know if everything is OK,” he said to me.

I spy... Twin 3-in. PVC schedule 40 combustion exhaust and intake lines greeted me as I descended the basement steps. A small puddle of water was in an etched spot on the concrete floor – directly under a dripping joint in the exhaust piping. Condensate is moderately acidic and had eaten away the surface – clearly this had been leaking for a long time. Following the exhaust piping to the next joint, someone had written “Not Glued” with a black marker and drew an arrow pointing to the 3-in. joint! Plastic hangar strapping was installed at 10-ft. intervals.

Three inch PVC schedule 40 pipe weighs 1.41-lbs. per foot and has an inside diameter of 3.068,” according to http://www.engineeringtoolbox.com/pvc-cpvc-pipes-dimensions-d_795.html. Plastic hangar strapping has a work-load weight limit of 20-lbs, according to www.oatey.com/doc/Plastic%20Hanger%20Strap.pdf. ‎The dry weight being supported was 14.1-lbs. As a plumber, you learn early-on to design for worst-case-scenarios and water weighs an average of 8.34-lbs. per gallon. Ten feet of 3-in. PVC has a 3.8-gallon capacity if flooded, which adds 31.69-lbs to the 14.1-lbs. pipe for a total of 45.79-lbs.

The IRC (International Residential Code) table P2605.1 lists a maximum horizontal distance of 4 feet between supports. Under our design for worst-case-scenario, each 4 feet of flooded 3-in. PVC will weigh 18.32-lbs, which will keep you under the maximum work-load of 20-lbs for plastic hangar strapping. (And that, my friends, also explains why their 4-in. PVC sanitary sewer line’s plastic strapping had broken.) 

At the other end of the basement, an indirect-vent (exhaust only) gas water heater with a 20-ft. long horizontal 3-in. PVC schedule 40 had just one loop of plastic hangar strapping for support and had compressed the 3”x2” rubber coupling installed at the exhaust blower’s vertical outlet. They had reduced the 3-in. exhaust blower’s outlet to 2-in. PVC and increased to 3-in. PVC midway on the riser. This too had been installed by the HVAC company that does not have any plumbers on staff.

But wait, it gets better! In addition to the PVC joints that were not glued together, the other joints had been glued together using CPVC cement and no primer had been applied. Several of those joints had cracked and partially separated!

My lawyer friend and his family had purchased the home four years ago and no one knows who labeled that exhaust vent “Not Glued.” It’s a miracle the piping had never separated to spew CO (carbon monoxide) into their home. At the final turn to exit the home, the PVC lines were installed at a sharp angle to clear the sill-plate. Given the deep snow accumulation, I next visited the exterior to see if the vents were above the 18 inches of snow.

Upon exiting the home, 90-degree elbows had been installed turned to vertical with two-foot extensions. The odd exit-angle required they extend both vents so that the off-center-pitch would allow the risers to be installed.

The HVAC company responsible for this mess likes to use their own branded thermostats, so they removed the first floor thermostat that also served as the brains for the zone damper system. Standard thermostats cannot be substituted. Solution? Cut the multi-conductor control cable, coil it up inside the zone damper control cabinet and lock all the zone dampers in their wide open position.

The flow-through humidifier’s vinyl drain-tube wrapped around the furnace to terminate in a ¾-in. PVC line, but neither was supported and had slipped apart. “Oh that? We had to turn off the humidifier because it floods the basement floor.”

The top of the furnace has been damaged from water escaping the cased A/C (air-conditioning) coil. No trap had been installed on the drain outlet, as is clearly illustrated in the manufacturer’s four-page I&O manual. Air rushing past the A/C coil’s drainage outlet creates a venturi-effect that prevents the free-flow of condensate, holds it back, and its shallow drain-pan overflows. Both the furnace and A/C blank warranty cards were in the same packet – never filled out or submitted.

An electronic air filter had been installed at ceiling level on top of the return-air plenum. The return-air plenum was actually a filter cabinet housing two throw-away filters – after the electronic air filter!      

Good grief Charlie Brown, it’s stunning to come across work like this installed by “professionals.” Whenever you encounter anything like this you need to CYA (cover your assets) by documenting your findings with pictures and put the details in writing. You touch it – you own it!

Let’s get together. Visit contractormag.com/forum to see the plumbing videos and pictures I posted of this potential minefield of an installation.

All Dave Yates material in print and on Contractor's Website is protected by Copyright 2014. 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].  

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