Relief Valve Leaks or SpillageCauses & cures for boilers, water heaters, water pressure tanks
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website. Leaks at temperature / pressure relief valves: This article describes the causes of leaks, drips, or discharges from pressure relief valves, temperature/pressure relief valves, or TP valves found on heating boilers, water heaters, or the simpler pressure relief valves found on water pressure tanks. We list the wide variety of possible TP Valve leaks and how to find and fix each of those problems, including how to fix a leaky pressure relief valve or leaky TP valve on a boiler, water heater, or water tank - what are the possible causes of leaks at these safety devices. Safety Hazard Warnings About Dripping or Leaking Pressure Relief Valves. How to use an expansion tank to relieve high water pressure. T&P Valves Installed on Gas Sidearm Heaters: special problems. Closed Hot Water System & Thermal Expansion Problems. We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. Leaky or Dripping Water Heater Pressure & Temperature Relief ValvesWatch out: a dripping or frequently spilling T&P valve is dangerous because those very leaks can eventually cause the valve to clog and then to fail to open when it should.If a relief valve becomes clogged and won't open when it should, the result could be a very serious explosion called a BLEVE EXPLOSION. So if you see water actually spilling or even if it's just dripping at the temperature/pressure relief valve on your heating boiler or water heater, the cause needs to be found and fixed promptly, and it may be appropriate to install a new T&P valve (also called TPR valve) after those repairs are complete. Here we list the reasons you may see water spilling or dripping out of the relief valve or out of the end of its discharge tube. Watch out: also, water spilling at a TPR valve can be scalding hot. Someone could get burned. Article Series Contents
Evidence of dangerous leaks and corrosion at water heater temperature/pressure safety valves Causes of leaky dripping Pressure/Temperature Relief ValvesTemperature & Pressure Relief valves may open, leak, or drip for a variety of reasons including:
Safety Hazard Warnings About Dripping or Leaking Pressure Relief ValvesWatch out: a dripping or frequently spilling T&P valve is dangerous because those very leaks can eventually cause the valve to clog and then to fail to open when it should.As our photo shows (above left), mineral salts left behind as hot water evaporates from the mouth of a pressure or temperature relief valve can completely clog the spring that is intended to allow the relief valve to open under excess (unsafe) pressure. The impaction of the relief valve spring with copper and calcium salts in this photo means that the valve is almost certainly not going to open should the heater's internal pressure become unsafe. The drip shown at the mouth of this relief valve demonstrates that a relief valve can drip and leak for a long time without anyone observing this dangerous condition. This relief valve needs to be replaced immediately and the cause for the valve's leakage also needs to be determined. Accidental or deliberately plugged Temperature & Pressure Relief ValvesWatch out: Never remove nor plug a pressure/temperature relief valve. This [water heater pressure/temperature relief] valve must be marked with the maximum set pressure not to exceed the marked maximum working pressure of the water heater. Install the valve into an opening provided and marked for this purpose in the water heater, and orient it or provide tubing so that any discharge from the valve exits only within 6 inches above, or at any distance below, the structural floor, and does not contact any live electrical part. The discharge opening must not be blocked or reduced in size under any circumstance. [1] [2] Technical note: why must the TP Valve point "down"? Take a look at the photo above. If a relief valve is dripping the deposit of minerals inside the valve will accumulate still more rapidly if the valve points to the side or upwards. The result is a clogged valve as we explain above - a dangerous situation that risks an explosion. See BLEVE EXPLOSIONS for an explanation of why a leaky or plugged TPR valve can cause a large catastrophic explosion. See WATER HEATER SAFETY for our complete list of water heater safety devices and water heater safety inspection advice. Closed Hot Water Systems & Thermal Expansion Problems - Why is the Water Heater Relief Valve Leaking?Watch out, serious safety hazards can be caused by dripping at the TP discharge line: often the dripping is caused by thermal expansion of hot water. For details please see THERMAL EXPANSION TPR VALVE LEAKS - an explanation of why thermal expansion leaks occur on hot water systems & what to do about it Also see HOT WATER PRESSURE EXPANSION RATE - for an explanation of just how much pressure increase to expect when heating water. In explaining why the relief valve on a water heater may be dripping T&P Valves Installed on Gas Sidearm Heaters: special problemsWatts Regulator Co. offers this explanation of T&P leak problems that may be encountered on gas fired sidearm heaters. [10] Question: What would cause an automatic T&P valve to open and close repeatedly when there is very little hot water in the storage tank?Reply: troubles at the gas sidearm heaterWith a sidearm gas heater a common problem is frequent T&P valve opening even though there is very little hot water in the hot water storage tank. That's because an overheated condition exists right at the sensor point of the T&P valve - most of the overheated water is "congested" at the top of the tank. This problem can be caused by undersized circulation piping between the sidearm heater and the water tank. Undersized piping between the sidearm heater and the tank (supply or return) amounts to a restriction of the circulation area (or volume). When this "too small" circulation area or volume is combined with a heater whose BTU input rate is higher than that undersized volume can carry, proper circulating does not occur through the tank nor through the sidearm heater coils themselves - the "congestion" referred to above occurs. In turn this congestion (think of it as a hot water traffic jam) causes overheating right where the T&P valve sensor is located, thus causing the valve to spill hot water repeatedly. In other words, hot water is accumulating at the T&P valve location rather than being distributed more evenly throughout the hot water tank. Because there is just a small volume of "too hot" water where the valve is located, the valve opens, spills the small amount of hot water, then is cooled and closes after just a short interval. To correct this condition install at least 3/4" piping, preferably not iron pipe, in the circulating loop. [The system we used for years used 1 1/4" diameter copper piping - Ed.] Non-ferrous piping is preferred to reduce the chances of clogging from rust debris - a clue that warns us that even 3/4" piped gas sidearm heaters can clog from rust or scale formation and will then exhibit this problem if the piping is iron. With an automatic gas storage heater installation, either the heater thermostat is acting abnormally (not shutting off when it should) or stacking temperature conditions are causing this TP leak. - paraphrased & adapted from information from the Watts Regulator Company. [10] ... Continue reading at THERMAL EXPANSION of HOT WATER or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX. Or see RELIEF VALVE LEAK FAQs - questions & answers about leaky temperature/pressure relief valves posted originally at the end of this page Or see these Recommended Articles
Suggested citation for this web pageRELIEF VALVE LEAKS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. Or see this INDEX to RELATED ARTICLES: ARTICLE INDEX to T&P RELIEF VALVESOr use the SEARCH BOX found below to Ask a Question or Search InspectApedia Or see INDEX to RELATED ARTICLES: ARTICLE INDEX to PLUMBING SYSTEMSOr use the SEARCH BOX found below to Ask a Question or Search InspectApedia ... Ask a Question or Search InspectApediaTry the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly. Search the InspectApedia website Note: appearance of your Comment below may be delayed: if your comment contains an image, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay. Our Comment Box is provided by Countable Web Productions countable.ca Technical Reviewers & ReferencesClick to Show or Hide Citations & References What to do if pressure relief valve is leaking?Leaking Relief Valve. Turn off the water heater breaker.. Shut off your water.. Empty the water heater by draining the bottom and water inside your home.. Remove the TPR valve and discharge tube by unscrewing with a wrench.. Replace with a new TPR valve and discharge tube.. Why would a pressure relief valve leak?Pressure relief and safety relief valves will leak if the valve isn't fully closed. This is a common problem in industrial settings where environments are often dusty or dirty. If there is any debris in the valve, it can obstruct the valve from fully closing, causing it to leak.
Is it normal for water heater pressure relief valve to leak?A slight leak may occur if your water heater's pressure relief valve has not been opened for a while, say a few years. While this leak is normal and may not be an indicator of a problem with the water heater system, you may need to replace the valve if the leak becomes more serious.
Is a pressure relief valve supposed to drip?When there is too much pressure inside the tank, the valve opens up to relieve this pressure and some water will drip out of it. This is normal, and indicates that the valve is functioning properly.
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