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Old 01-16-2011, 03:28 PM   #1
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Hot Water Tank and Pressure Help

I live in an area where many main breaks happen. I live on a hill with 4 other homes (my home is the first one at the top). The water pressure is so great, that I had to buy the heavy duty water hoses as all the others would SPLIT. the hose nozzles all split where the plastic is bonded together due to the pressure and a few of my faucets leak. I have no Pressure Regulator in my house. I just purchased a Pressure Gauge that fits on a hose bib outside. I measured twice and the pressure is between 80 and 100PSI. So, there is Problem 1.

Problem 2. When a Main Water Break happens, the water in my Hot Water Tank flows back out of the house, burning up the Top Element. This just happened to me a week ago. If I'm home when the water goes out, I can kick the breaker to the HW Tank and all is ok. If I'm not home (like this case), I have an element burn up due to low water in the tank. I was told to buy a Regulator and a Check Valve by a Plumber (friend) who would install it. However I read that due to heat expansion in the tank, you should have an Expansion Tank on your Hot Water Tank.

Questions: Obviously, I need a Pressure Regulator due to 80 - 100PSI. With a Regulator, do I still need a check valve, or will the Regulator prevent waterflow in only one direction as well? If I need a check valve as well, where is it to be installed? What about the Expansion Tank? Will this be necessary with a Regulator and Check Valve? I'd assume if I put in a Check Valve, an Expansion Tank would be a must since the expanded water would have no where to 'expand'. But, will an Expansion Tank then negate the need for a Check Valve...does it prevent the water from the HW tank from flowing back out, etc. etc. I want to be sure I understand before I have a Plumber come do this work. I'm in an area where Building Code is NOT enforced and most work is NOT performed under code (electrical, plumbing, etc.). I purchased my house new and have made many changes to the electrical (such as the electrician using 14AWG and 20A breaker. However, the person may not have been a licensed electrician since there are no mandatory inspections, etc. in my rural area).

Thanks in advance for any help. I'd like to get this work done as soon as possible. My friend can physically do all the work just fine, I just want to make sure I put in the correct devices in the correct place.


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Old 01-16-2011, 08:43 PM   #2
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An expansion tank will not prevent water from being sucked out of a nearby water heater.

If you install a check valve on the incoming water, then you should have an expansion tank above the water heater.

You could put a vacuum breaker in the cold water line just before it enters the water heater and that would prevent sucking water out.

Fire engine pumpers have been known to put so much suction on water lines that water heaters in nearby homes collapsed (imploded). Vacuum breakers (they're about the size of water heater pressure/temperature relief valves) prevent that.


The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 01-16-2011 at 08:47 PM.
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Old 01-17-2011, 09:25 AM   #3
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First off, you need an expansion tank for your system regardless of whether you have a backflow preventer (check valve). I have well water, so my expansion tank is on the cold water inlet line adjacent to the pump controller, however you are on city water, so your expansion tank is going to be located near the water heater. The exact location will be determned by the plumber who installs it, or if you install it read the directions from the tank manufacturer.

Second, the vacuum breaker is mandatory code in my area, however it DOES NOT prevent water from draining out of the tank in the event of loss of pressure on the mains, quite the opposite. The purpose of a vacuum breaker is to allow air to enter the tank in the event of loss of pressure on the mains. This will prevent the tank from collapsing, however it will allow a siphon to form allowing your tank to drain, thereby allowing your top element to crisp as now. The vacuum breaker is installed on the cold water side of the tank where the water line enters.

Yes you need a pressure regulator, 80-100 psi is too high for most fixtures, 60-80 psi is a common rating. The pressure regulator is typically installed in an accessible location inside your house immediately after the water line enters. I believe that there are combination models of pressure regulators that include an integral backflow preventer, however you can also install a backflow preventer (check valve) separately in line with the regulator. My boiler has a separate check valve (Watts) and pressure regulator (Watts) that drops the pressure to about 15 psi and also prevent boiler water from flowing backwards into the potable water line. The particular pressure regulator I used could have been purchased as a combination check valve/pressure regulator, however I elected to put separate devices on the system, along with a quarter turn ball valve to shut the water down.
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