Inspection Findings on a Potable-Water Retrofit
You are asked to inspect a retrofit before the homeowner's final payment. The system preheats potable water through a single-wall copper coil immersed in a 100-gal tank that also contains 30% propylene glycol from the collector loop. The collector loop's 150-psi pressure relief valve discharges through 22 ft of 1/2-in. copper with four elbows into the crawlspace, ending 3 in. above the soil. The four collectors are on a 7/12 roof of a three-story house; the only access is a 28-ft extension ladder, and no anchors are installed. The expansion tank is unsupported on flexible hose, the controller is not listed, and the collector array's piping is not bonded. The owner wants a sign-off and asks which items are "must-fix today."
1. Rank the deficiencies by risk and identify which items justify withholding sign-off.
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Withhold sign-off on four items:
Single-wall heat exchanger between glycol and potable water - highest risk. A pinhole or corrosion failure allows heat-transfer fluid into drinking water with no detection. Most model plumbing codes require a double-wall heat exchanger with a vented leak path between walls when the heat-transfer fluid is not potable; a single-wall coil relies on the fluid being non-toxic, which is a weak defense for a pressurized loop. Correct before any use.
Relief valve discharge into the crawlspace - code violation and a scald/burn and structural-damage hazard. Discharge must terminate to a safe, visible location: within about 6 in. of a floor, outside, or to an approved drain, and must not be trapped or discharge where nobody will see it. A 150-psi glycol loop releasing under a house is unacceptable.
Unsupported expansion tank on flexible hose - mechanical failure and flooding risk. It needs rigid support, an isolation valve, and a drain.
Unbonded collector piping - electrical hazard. Metal piping and collectors need bonding per the electrical code and manufacturer instructions; a fault or nearby strike can energize the array.
Lower priority but still required before final: listed controller, fall protection for service, and labeling of the loop, valves, and relief device.
2. For each must-fix item, state the specific corrective action and what you would verify at re-inspection.
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Heat exchanger: replace the single-wall coil with a double-wall, vented heat exchanger rated for the loop pressure and temperature, or convert the system to a drainback design using potable water in the collector loop. Verify: nameplate rating, double-wall construction with a visible leak path, pressure test of both sides, and no cross-connection anywhere in the potable side.
Relief discharge: repipe in rigid pipe the same size as the valve outlet, with no reducing fittings, no trapped sections, and a downward termination within about 6 in. of the floor or to an approved drain, in a place the homeowner can see. Verify: full-size pipe, no valves or plugs, no freeze-prone route, and a drip-pan or drain if discharge could damage finishes.
Expansion tank: mount on a bracket or strap to structure, with a isolation valve and drain, precharge set to the correct cold fill pressure. Verify: no hose supporting the weight, tank not at a high point where it becomes an air trap, and precharge checked with a gauge.
Bonding: bond the collector frames, piping, and tank to the grounding system per the electrical code and manufacturer instructions. Verify: an actual continuity test, not just a visual clamp, and a record of the reading.
Also verify the controller is listed and labeled for solar thermal use, and that the system is labeled with fluid type, pressure, and relief setting.
3. The owner asks whether a fall-protection system is really required for a three-story roof when the crew only goes up "once a year." How do you answer, and what is your recommendation?
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Frequency does not change the hazard. A fall from a three-story roof is likely fatal, and the annual service visit is exactly when it happens - someone leaning over the edge to check a sensor or clear snow. At that height, fall protection is required for work at height under occupational safety rules, and the manufacturer's installation instructions and good practice both assume a safe service access.
Recommendation: • Install permanent roof anchors rated for fall arrest, or a guardrail system around the service side, engineered for the roof structure. • Provide a safe access route - a fixed ladder with a cage or a roof hatch with a grab rail - not a loose extension ladder against a gutter. • Keep a written fall-protection plan with anchor locations, harness and lanyard specs, rescue-at-height procedure, and training records. • Require the service technician to use the system and document it on every visit.
If the owner refuses, put the recommendation in writing, note the residual risk, and state that future service will be scheduled only with fall protection in place. That is not overreach: it is the difference between a service call and a fatality, and it belongs in the same conversation as the relief valve and the heat exchanger, not after the check clears.