Hot Water Heater

steve_6

i agree, check for a pressure reducing valve. it's a bell shaped valve usually located right after your water meter. if you have one you should have an expansion tank installed on your hot water tank

Bob R.

Hot Water Heater

We installed a new hot water heater two years ago and it had been working fine until the pressure release valve started leaking. I replaced the valve but it is still leaking through the overflow pipe and the hot water pressure is not as strong and when originally installed. What could be causing this problem?

Jackchips

Perplexing.

It sounds like your building pressure in the tank and that is causing the relief valve to discharge. Is there any chance there is a valve on the outlet of the heater that is partially closed and that is limiting the pressure out to the system but building up in the heater?

Steve Paul

Stratification is the culprit

The water haeters thermostat is near the bottom of the tank, as the water is heated it rises towards the top of the tank and is replaced by cooler water. This is convection. The cooler water tells the thermostat to fire the flame and heat the water. As each heating/rising cycle is completed you will have varying temperature levels or strata in the tank. As you go higher the temperature increases. It is not inconceivable that at the relief valve level the temperature can approach 210 degrees. This will cause the relief valve to open. the cure is to turn down the thermostat setting a few degrees. Try it, you'll like it.

Mark Hunt

The water pressure


coming into your house may have changed. Has anyone added a pressure reducing valve or flow check device recently?

Has there been any work on the water main? You may want to give the municipality a call and check on this.

Hope this helps!

Mark H

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Frank Humr

Hot water heater

You should install an Ex-troll expansion tank on the hot water side of the tank via a "T" in the copper riser. Make sure the tank is rated for domestic hot water.

hot_rod

Boyle's Law

Bob,

Here's a copy of an article I wrote for Contractor that deals with your issue.

Thermal Expansion Tanks & Boyle?s Law
Copyright - Dave Yates

You?ve seen these first hand, the water heaters with water lines extending upwards at odd angles, like a bow-legged bronco buster. A collapsed flue tube and another water heater gone to an early grave. A sure sign of thermal expansion gone unchecked.

The causes varied a bit. Some from pressure reducing valves, others from backflow preventers and a few from plugged relief valves! In each case, a properly sized thermal expansion tank would have prevented premature replacement of the customer?s water heater and would have kept the relief valves from leaking. The plugged relief valves gave me nightmares. Ignorance might be bliss, but dead is permanent. I wish relief valves were made with either no threads or vacuum/vent safety features.

In the beginning, when backflow preventers were first introduced to the city water service lines, there was a flood of calls regarding leaking relief valves and failed water heaters. The market-place was inundated with a myriad of choices for thermal expansion tanks and darn few of them came with adequate instructions regarding proper sizing or the relationship between thermal expansion of the water and the air volume/pressure of the bladder tanks. Several models were limited to less than the 150 PSI maximum working pressures of water heaters and had to have their own relief valves. Even today, it remains difficult to ascertain the truth regarding proper sizing of a thermal expansion tank and it is a subject that stirs heated debate between plumbers, distributors and homeowners.

Most manufacturers of thermal expansion tanks offer two basic residential sizes: 2 and 4.5 gallon bladder tanks. These are shipped with a factory air charge of 40 PSI. If you visit their web sites, or obtain the installation sizing literature for the majority of these tanks, you will find that the smaller tank is rated to handle 40 gallon water heater expansion rates per their charts. Some base this upon the assumption of a fixed water pressure and fifty degree rise in temperature. The only problem is that their charts are based upon pie-in-the-sky field conditions that are typically exceeded under actual use. York Water Co. recorded service lines temperatures have ranged from 34 to 80 degrees.

According to the 1993 BOCA Commentary (P1508.7) and the 1997 International Plumbing Code Commentary (607.3), 40 gallons of water heated from 45 to 145 degrees will have 1 gallon of thermal expansion, a ratio of 40:1. The argument put forth by some manufacturers and espoused by many in our trade, is that you need simply increase the tank air pressure to match the incoming water pressure on the smaller 2 gallon bladder tanks. Aside from the fact that a steady stable pressure state hardly ever exists in the real world and that 50 degrees is seldom the maximum difference between street and final temperatures, we can determine the actual working conditions our customers? potable water systems will be facing with the aid of Robert Boyle, an English chemist of old. Boyle?s law states that as the volume of air in an air-tight vessel is compressed, the pressure will rise.

Let?s set forth the conditions we?ll be facing on two theoretical identical properties. The incoming water pressure will be a constant 70 PSI, the water heaters will be 40 gallons, there will be no expansion within the water heater tank or in the distribution piping, there are absolutely no leaks or dripping faucets and not one bubble of air exists in the entire system. A double-check backflow preventer is installed just after the meter.

For example #1, let?s say that the installers are too busy, lazy or just plain didn?t give a hoot and decided to install their respective thermal expansion tanks as shipped from the factory with the 40 PSI air charge. The only difference will be the size of their tanks. Here, take a look at ?Chart A? to see what will happen to the tanks as the pressure climbs to the system?s steady state of 70 PSI. Keep Boyle?s law in mind and realize that the air pressure must rise as its volume decreases and will equal the water pressure at all times.

So, what will occur as we introduce thermal expansion into these two tanks? Look at ?Chart B? to see what occurs in these two tanks as the pressures begin to climb from the stress of thermal expansion. Bear in mind that the weights of water listed in ?Chart A? must be added for the total weight of water now in these tanks. Knowing that a gallon of water weighs 8.33 pounds and checking the 2 gallon tank, 145 PSI column, reveals that this tank is inadequate and should never be used in this application. The larger tank will peak at slightly under 120 PSI after one gallon of thermal expansion. House #1 will experience thermal stress and possibly an expensive call-back for a ruptured bladder or damaged water heater unless the additional expansion can be absorbed by the system components. Not a very desirable situation and certainly less than professional.

For example #2, let?s agree that these two mechanics both believe in adding sufficient air to their thermal expansion tanks to match the 70 PSI incoming street pressure. Checking ?Chart C? reveals that the 2 gallon thermal expansion tank continues to be undersized, even at 145 PSI. The larger 4.5 gallon tank easily accommodates the one gallon of thermal expansion at slightly less than 100 PSI.

For less than $10.00 difference in cost between the two tanks, which one do you think is a better buy? Which one best serves your customers? needs and protects the investment in their water heater? Don?t forget to adequately support the weight, especially on horizontal installations. Think fulcrum.




To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Davel_3

Hot water heater

Check the house PRV the incoming pressure is one easy thing to check and will cause the relief valve to leak.Good luck