Your Attic Water Heater Is Fine. Check the Pan Drain.
Every tank water heater eventually fails. Whether that is an inconvenience or a ceiling replacement is decided entirely by a drain line most homeowners have never looked at.
August 27, 2026 · 6 min read
Murphy built out in a tight window — most of the city went up between the late 1990s and the mid 2000s — and it built out with large two-story houses. In a house that size, the builder puts the water heater where it costs the least floor space, and in Collin County that means the attic.
It is a perfectly reasonable place for it, with one condition attached. Every tank water heater fails eventually. They are steel vessels holding forty or fifty gallons of hot water, and when the tank corrodes through, it empties. In a garage that is a wet floor. In an attic above a finished second storey, it is drywall, insulation, flooring and whatever is below that.
What is supposed to be up there
Three things, and all three need to actually work:
- A drain pan under the heater, sized so the tank sits inside it rather than overhanging the edge.
- A drain line from that pan, sloped continuously downhill, terminating somewhere outside where a discharge is visible.
- A temperature and pressure relief valve on the heater with its own discharge pipe, routed either into the pan or separately to outside.
That is the whole system. It is not complicated, and it fails constantly, because nobody looks at it between the day it was installed and the day it is needed.
What we actually find in Murphy attics
A pan with no drain at all
More common than it should be. The pan is there, and it holds perhaps two gallons before it overflows. A failed tank puts fifty gallons into it. The pan buys you about ninety seconds.
A drain line that goes uphill
Usually the result of the heater being replaced at some point by somebody who reconnected the existing line without checking the fall. Water does not climb. The line looks connected and it will never carry anything.
A drain line that terminates in the attic
We have found pan drains that run three feet and stop, and pan drains routed into the HVAC condensate line — which is legal in some places and a bad idea everywhere, because a blocked condensate line now backs both systems up into the same attic.
A pan full of rust
A galvanized pan that has held standing water for years has corroded through at the bottom. It is present, it is under the heater, and it is not a pan any more.
The T&P valve is a separate thing
People conflate the pan drain and the relief valve discharge. They do different jobs. The pan catches a leaking tank. The temperature and pressure relief valve opens when the tank exceeds safe pressure or temperature and discharges hot water deliberately.
A T&P valve that is weeping is telling you something — usually that system pressure is too high, sometimes that the thermostat is overshooting. In a Murphy house it is worth checking the house pressure at a hose bib before assuming the heater is at fault. A failed pressure reducing valve or a waterlogged expansion tank produces exactly this symptom.
Leak detection worth having
A water alarm in the pan costs very little and will wake the house up. A leak-detection shutoff valve costs more and closes the water supply to the heater automatically when it detects water in the pan, which is the difference between a small mess and a large one when the failure happens while you are away.
For an attic installation over finished living space, that is money well spent. It is the same logic as a smoke detector: cheap insurance against an event that is unlikely in any given year and expensive when it happens.
When to replace rather than wait
Murphy's housing stock is largely 20 to 25 years old now. If your water heater is original, it is well past the point where replacement on your schedule beats replacement on its schedule. Read the serial number on the data plate — it encodes the manufacture date — or call us and we will decode it for you over the phone.
Family-owned, based in Rockwall, and Collin County is on our daily route. TX Master Plumber TXM11693, TX HVAC TACLB2360E. (469) 338-5533.
Frequently asked
Is it safe to have a water heater in the attic?
Yes, provided the pan, the pan drain and the relief valve discharge are all correctly installed and actually functional. The installation itself is not the risk — an unmonitored, undrained pan over finished living space is.
How do I know if my pan drain works?
Pour a bucket of water into the pan and watch the exterior termination. Water should arrive within seconds. If you cannot locate an exterior termination at all, the line either does not exist or discharges somewhere it should not.
My water heater relief valve keeps dripping. What does that mean?
Most often it means system pressure is too high rather than that the heater is faulty. Check the pressure at an outside hose bib — anything over about 80 psi points at a failed pressure reducing valve or a thermal expansion tank that has lost its charge, and fixing that usually stops the dripping.