Water Heater Leaking or Relief Valve Dripping in Hawaii: Causes, Repair or Replace
Short answer: where the water comes from tells you what to do. A relief valve that drips now and then usually means pressure is too high (thermal expansion or high street pressure), which is fixable. A relief valve that gushes hot water means the tank is overheating, so turn the power or gas off now. Leaks at the pipe connections, the valve threads or the drain valve are repairable. Water coming out of the tank itself, or seeping where the relief valve's fitting is welded to the tank, means the heater needs replacing. Need it looked at? Call (808) 772-0705 or use the form below.
Last updated October 28, 2026. Hawaii Plumbing Line provides this as general information. Code sections and utility rules come from the sources listed at the bottom.
First 10 minutes
- Do not plug, cap or remove the relief valve, even if it keeps dripping. It is what stops a tank from overheating or bursting.
- Is it hot water coming out fast, or steam? Turn the heater off: the breaker for an electric or heat pump unit, or the gas control to off for a gas unit. Keep clear of the discharge pipe.
- Is water pooling? Close the cold-water valve on the pipe going into the top of the heater. If you can't find it or it won't turn, shut the main. See where your shut-off valve is.
- Find the source with a dry paper towel: wipe the top connections, the relief valve and its pipe, the drain valve at the bottom, and the floor under the tank.
- In a condo, tell your building manager right away and take photos. See who pays for a condo leak in Hawaii.
Where is it leaking? Repair or replace
| What you see | Usual cause | Repair or replace? |
|---|---|---|
| Relief valve pipe drips on and off, often after heating or overnight | Pressure creeping past 150 psi from thermal expansion or high street pressure | Repair: fix the pressure (expansion tank, pressure reducing valve), then replace the valve if it no longer seals |
| Relief valve suddenly dumps a lot of very hot water | Tank overheating. A. O. Smith says this means a failed thermostat on a standard tank; on solar, check the controller and sensors | Repair, urgently. Power off until fixed |
| Water at the threads where the relief valve screws in | Failed thread seal | Repair: remove and reseal |
| Seeping around the fitting welded to the tank (the spud) | Tank fitting failed | Replace. A. O. Smith says the spud is not repairable |
| Drips at the hot or cold connections on top | Loose or corroded connector, or corrosion where copper meets steel | Repair: new connectors or dielectric fittings |
| Drip from the drain valve at the bottom | Worn drain valve or debris in its seat | Repair: cap it or replace the valve |
| Water under the tank with dry fittings above, rust on the jacket, rusty hot water | Tank corroded through | Replace |
| Water near a heat pump unit | Often the condensate drain, which is normal water from the air, not a tank leak | Clear or reroute the condensate line |
Why relief valves drip in Hawaii homes
A standard tank's combination temperature and pressure (T&P) relief valve opens at 210°F or 150 psi. A slow drip almost always points to pressure, and in Hawaii there are two usual suspects:
- High street pressure. Honolulu's Board of Water Supply rules (Sec. 2-210) say that when the supply pressure is higher than your fixtures are designed for, the owner must install and maintain pressure reducing and relief valves, and BWS is not liable for damage from pressure or failed regulators. Hawaii County's water rules say the same. Honolulu's plumbing code (ROH Chapter 19) adopts the 2018 Uniform Plumbing Code, which requires a pressure regulator where static pressure is above 80 psi. Homes downhill from a reservoir can see high pressure, and pressure reducing valves wear out.
- Thermal expansion in a closed system. Water expands when it heats. If a check valve, backflow preventer or pressure reducing valve stops it from flowing back to the street, pressure climbs with every heating cycle. The Uniform Plumbing Code (608.3) requires an approved, adequately sized expansion tank on that kind of system. Hawaii County's rules (Section 3-15) also require a relief valve on the hot side wherever a check valve or pressure reducing valve sits between the meter and the heater. An expansion tank that was never installed, or whose air charge is gone (it feels heavy and sounds full when tapped), lets pressure spike again.
A quick check: a plumber (or you, with a pressure gauge on a hose bib) can read the house pressure in the morning and again after the heater runs. A reading above 80 psi, or one that climbs sharply after heating, tells you where the problem is. Replacing only the relief valve without fixing the pressure usually brings the drip back.
Solar water heaters
Solar is common in Hawaii, and solar tanks run hotter than electric ones. Hawaii Energy's solar program handbook calls for a non-adjustable 210°F / 150 psi T&P valve on the storage tank, a separate 125 or 150 psi pressure relief valve at the roof collectors, and a backup heating thermostat set between 110 and 120°F. UH's building maintenance course notes that expansion tanks are installed mainly on solar systems.
- Dripping at the roof collector valve: pressure is building in the collector loop. That is roof work for a licensed contractor.
- Tank relief valve discharging on sunny afternoons: the tank is likely overheating. A failed sensor, controller or check valve is a common cause. Have the whole system checked, not just the valve.
- Replacing a solar tank? Hawaii Energy's solar rebate asks for a permit number. See our solar water heater guide.
Is the relief valve discharge pipe right?
Under the Uniform Plumbing Code, the discharge pipe must be full size, drain by gravity with no trap, valve or threaded end, and end outdoors 6 to 24 inches above the ground or at an approved indirect drain where you can see it. It must not drain into the water heater pan. A pipe that is capped, kinked, or ends hidden in a wall or ceiling is a safety problem; ask a plumber to correct it when the valve is serviced.
Repair or replace: how to decide
- Age. The serial number on the label encodes the manufacture date. Published Oahu guidance puts tank life at roughly 8 to 12 years.
- Cost. Allens Plumbing, an Oahu company, publishes $150 to $500 for typical repairs (relief valve, thermostat, element) and $1,200 to $3,500 for a tank replacement. If a repair costs more than about half of a new unit, replacing usually makes more sense. See our water heater replacement cost guide.
- Water and corrosion. Oahu water ranges from soft to very hard (25 to 300 ppm) depending on which wells are serving your address; BWS Water Quality at (808) 748-5840 can tell you yours. Very soft or softened water eats the tank's anode rod faster. An anode check every few years can add life to a newer tank.
- Rebates if you replace. Hawaii Energy lists in-store rebates of $500 or $700 on ENERGY STAR heat pump water heaters (Oahu, Maui County, Hawaii Island), and KIUC offers $500 on Kauai. See is a heat pump water heater worth it in Hawaii?
- Permits. In Honolulu, like-for-like valve work generally falls within the $2,500 small-repair exemption, but replacing the heater generally needs a permit. See our permit guide.
Questions to ask your plumber
- What is my house water pressure, before and after the heater runs?
- Is my system closed (check valve, backflow preventer or pressure reducing valve)? Is there a working expansion tank, and is its air charge set to my house pressure?
- Is the leak at a repairable part, or at the tank or its welded fittings?
- Does the discharge pipe meet code?
- If I replace, does the quote include the permit, haul-away, expansion tank and any pressure reducing valve work?
Want us to take a look?
Call (808) 772-0705 or use the form below. Tell us your island and town, the type of heater (electric, gas, heat pump or solar), its age if you know it, and where the water is coming from. A photo of the label and the leak helps. Always check a plumber's license before work starts.
Frequently asked questions
Is it normal for a water heater relief valve to drip?
No. The relief valve is a safety device and should stay dry. A slow drip usually means pressure in the house is climbing past the valve's 150 psi rating, most often from thermal expansion in a closed system or high street pressure. A burst of very hot water means the tank is overheating. Either way, find the cause instead of just replacing the valve.
Can I plug or cap a dripping relief valve?
Never. A plugged or capped relief valve removes the only protection against a tank overheating or over-pressurizing. Put a bucket under the discharge pipe, turn off the power or gas if the water is very hot, and call a plumber.
Why does my relief valve drip at night or after a shower?
When the heater warms a full tank of cold water, the water expands. If a check valve, backflow preventer or pressure reducing valve stops that extra water from going back to the street, pressure rises until the relief valve lets some out. An expansion tank that is missing, undersized or waterlogged is the usual fix. The Uniform Plumbing Code that Honolulu adopted requires one on a closed system.
My water heater is leaking from the bottom. Can it be repaired?
If the water is coming from the tank itself, no. A rusted-through or cracked tank cannot be repaired and needs replacing. Before you decide, check that the water is not running down from the top connections, the relief valve pipe or the drain valve, which are all repairable.
How much does it cost to fix a leaking water heater on Oahu?
One Oahu company, Allens Plumbing, publishes $150 to $500 for typical repairs such as a relief valve, thermostat or element, and $1,200 to $3,500 to replace a tank unit. A common rule of thumb is to replace when a repair would cost more than half of a new unit, especially past 8 to 10 years. Ask for both prices in writing.
My solar water heater relief valve is dripping on sunny days. Why?
Solar tanks can get much hotter than an electric tank. On sunny afternoons a failed sensor, controller or mixing valve can let the tank reach the relief valve's 210°F setting, or heating can push pressure up. Hawaii Energy's program rules call for a 210°F / 150 psi relief valve on the tank and a separate 125 or 150 psi relief valve at the roof collectors. Have the whole system checked, and leave roof work to a licensed contractor.
Do I need a permit to replace a relief valve or water heater in Honolulu?
A like-for-like valve repair generally falls within Honolulu's $2,500 small-repair permit exemption. Replacing the water heater itself generally needs a permit. See our Hawaii plumbing permit guide.
Sources
- A. O. Smith Technical Bulletin 52: Leaking temperature and pressure relief valve (210°F / 150 psi ratings; seeping at the welded tank spud is not repairable; weeping = thermal expansion; large hot discharge = thermostat failure)
- Honolulu Board of Water Supply Rules and Regulations (PDF) (Sec. 2-210 Pressure Conditions: owner installs and maintains pressure reducing and relief valves; BWS not liable for pressure damage)
- Hawaii County Department of Water Supply Rules, effective December 25, 2020 (PDF) (Section 3-3(3) pressure reducing and relief valves; Section 3-15 relief valve required when a check valve or pressure reducing valve is between the meter and a water heater)
- Revised Ordinances of Honolulu Chapter 19: Plumbing Code (Ord. 22-25 adopts the Hawaii State Plumbing Code based on the 2018 Uniform Plumbing Code)
- Uniform Plumbing Code 608.2: Excessive water pressure (regulator required above 80 psi static)
- Uniform Plumbing Code 608.3: Expansion tanks and combination temperature and pressure relief valves
- Hawaii Energy: Solar Water Heating Program Handbook (PDF) (collector pressure relief valve 125 or 150 psi; tank T&P valve 210°F / 150 psi, non-adjustable; backup thermostat 110 to 120°F)
- University of Hawaii OER: Building Maintenance, Water Heating (expansion tanks; dielectric and lined nipples)
- Honolulu BWS: Water quality FAQ (Oahu hardness 25 to 300 ppm, varies by address; Water Quality (808) 748-5840)
- California Energy Commission docket: Impacts of water quality on residential water heating equipment (PDF) (softened water speeds anode consumption and tank corrosion)
- Allens Plumbing: Water heater repair vs replacement, an Oahu homeowner's guide (Feb. 6, 2026) (published Oahu ranges: repairs $150 to $500, replacement $1,200 to $3,500; 50 percent rule)
- Hawaii Energy: Water heating rebates