Newer-Home Plumbing in South Overland Park: PRVs, Expansion Tanks and Why Your Relief Valve Drips
By FlowRight Plumbing of Overland Park · · Sources linked in each section
If the relief valve on your water heater drips, or there’s a small puddle at the end of its discharge pipe, the valve may be doing exactly its job. In many newer homes, the real issue is pressure, and the fix is upstream of the valve.
Two parts that work as a team
A pressure-reducing valve (PRV) sits on the main water line and lowers street pressure to a level that’s safer for fixtures, hoses and appliances. Many PRVs, along with backflow devices and check valves, also stop water from flowing back toward the street. That creates a closed system.
In a closed system, water that expands as your water heater heats it has nowhere to go. Pressure climbs every time the heater runs. A thermal expansion tank, a small tank with an air bladder near the water heater, gives that extra volume somewhere to go.
What the code requires
Overland Park adopted the 2024 International Plumbing Code effective July 1, 2026 (Ordinance BC-3499), without amending these sections. The IPC requires a pressure-reducing valve where static water pressure exceeds 80 psi, and requires a means of controlling thermal expansion where a check valve, backflow preventer or pressure-reducing valve makes the system closed. When a water heater is replaced under permit, the inspector looks for both.
Source: Overland Park Ordinance BC-3499 (2024 International Codes, effective July 1, 2026). Checked October 2026.
What a dripping relief valve is telling you
Replacing just the relief valve treats the symptom. If pressure is the cause, the new valve will drip too.
- The expansion tank is missing, undersized, or its bladder has failed (a waterlogged tank)
- The PRV is failing and letting street pressure through
- The water heater thermostat is set very high
- Less often, the relief valve itself is worn
Simple checks you can do
- Screw a pressure gauge onto a hose bibb and read the static pressure. Check it again after the water heater has been heating for a while without water being used. A big rise suggests failing expansion control.
- Tap the expansion tank: an air-charged tank sounds hollow at the top. A tank that sounds full of water all the way up may have a failed bladder.
- Never cap or plug a relief valve or its discharge line. It’s a critical safety device.
Why we see this in south Overland Park
South Overland Park is much newer than the north side of the city. In Census estimates, the median home in ZIP 66221 was built in 2007 and in 66224 in 2003, compared with 1965 in 66204 up north. Newer homes are more likely to have a PRV and a closed system from day one, and expansion tanks wear out, so a house that was fine when it was built can develop the problem years later.
| ZIP | Area (approx.) | Median year built | 2000 or later | 1980–1999 | 1960–1979 | Before 1960 |
|---|---|---|---|---|---|---|
| 66204 | North Overland Park (Downtown OP area) | 1965 | 15.3% | 13.9% | 30% | 40.8% |
| 66212 | Central-north Overland Park | 1970 | 6.7% | 19.5% | 57.3% | 16.5% |
| 66210 | Overland Park (College Blvd corridor) | 1986 | 16.7% | 59.3% | 21.6% | 2.5% |
| 66213 | South-central Overland Park | 1995 | 29.5% | 64.4% | 4.2% | 1.8% |
| 66223 | South Overland Park | 2001 | 52.1% | 45.4% | 2% | 0.4% |
| 66221 | South Overland Park (our base) | 2007 | 73% | 21.4% | 2.8% | 2.8% |
| 66224 | Far south Overland Park | 2003 | 62.2% | 30.8% | 6.2% | 0.7% |
| 66085 | Stilwell and far south Overland Park | 2002 | 53.3% | 24.3% | 18% | 4.4% |
Source: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, tables B25034 and B25035 (via Census Reporter). Checked October 2026.
Frequently asked questions
Can I add air to my expansion tank?
Expansion tanks are pre-charged to match house pressure, and setting it correctly requires isolating and draining the tank. If the bladder has failed, adding air won’t fix it.
What water pressure is too high?
The plumbing code requires a pressure-reducing valve when static pressure exceeds 80 psi. Many homes run around 40–60 psi.
Related pages
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