Pressure Test Drops on a Galvanized-to-PEX Repipe
You are repiping a 1958 split-level with PEX-A. The existing 3/4 in galvanized steel service enters the basement, and the homeowner wants the galvanized removed and PEX throughout. Your transition is a 6 in copper nipple soldered to a brass PEX manifold, then PEX-A to the fixtures. You use 95/5 lead-free solder and water-soluble flux, and you assemble the copper with a propane torch. For the test, you fill the system with water, bleed the air, and pressurize to 100 psi. Two hours later the gauge reads 72 psi. The water heater is connected, the basement is 58°F, and the crawlspace branch runs 25 ft with no heat. A soap test shows a weeping joint at the third elbow, and you find a pinhole in a short section of existing copper near the water heater. The inspector requires a 100 psi, 2 hour test.
1. Is the 28 psi drop by itself proof of a leak? Explain what else can move a gauge and how you would isolate the cause.
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A 28 psi drop is significant, but the gauge reading alone does not prove a leak. Temperature change, trapped air, a leaking test valve or gauge, and the connected water heater can all move the reading. The soap bubbles at the elbow do confirm a leak there. Isolate sections with test balls or valves, use a calibrated gauge, and re-test after repairing the leak. A temperature drop in the 25 ft unheated crawlspace can contract water and lower pressure; record water temperature and allow the system to stabilize. If the gauge continues to fall after isolation, the leak is in that section. If it does not, check the test rig, valves, and water heater connections.
2. List the likely causes of the weeping soldered joint and the pinhole, and describe the repair you would make.
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A weeping solder joint usually comes from water in the pipe, which turns to steam and blocks capillary flow, or from insufficient heat, overheating that burns the flux, dirty or wet pipe, too much flux, or movement while the joint cools. Repair it by draining and drying the line, cutting out the joint, cleaning to bright metal, re-fluxing, and soldering with a dry pipe, or by using an approved press fitting. The pinhole near the water heater suggests aggressive water, high velocity, flux residue, or galvanic corrosion. Cut out the damaged section and replace it with new copper or PEX, then check water chemistry. Do not simply solder over a pinhole.
3. Describe the correct transition between the copper, the galvanized service, and the PEX, including any dielectric protection and support/protection requirements.
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Connect PEX to copper with an approved brass or engineered-plastic transition fitting. Connect copper to galvanized steel with a dielectric union or an approved dielectric nipple. Direct copper-to-steel contact creates a galvanic cell; the steel becomes the anode and corrodes. Use dielectric protection at the water heater and at the steel service entry. Support PEX at the required intervals and protect it from UV, abrasion, and freezing in the 25 ft crawlspace; insulate or heat-trace as needed. Keep PEX at the manufacturer's required clearance from the flue and use only listed fittings. Pressure-test the completed assembly before closing the walls.