Expansion tank for boiler but not Domestic hotwater,Why?

Jason Roberts

If my Hot water boiler works at 150 degrees and my domestic hot water gas heater works at 140 degrees why do I need an expansion tank for the boiler and not the domestic tank.

chuck shaw

closed loop

Your heating system is a closed loop. When water heats, it expands, and the tank asorbs the expansion. With domestic hot water, the expansion goes either, against the blader in the well tank, or backwards out the water meter. In areas where self checking meters are used, this can become a hazard, and a tank, made and presurized for domestic use is installed. Massachusetts code requires them to be as close to the water meter as is pratical.

Also, unless you have a mixing valve on your domestic hot water tank, I would advise you to turn the water temperature down to avoid possible injuries from scalding.

Hope this helps

Chuck Shaw

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

kevin coppinger_4

that is a good....

question! You might need one! If you are on City/town water and there is a backflow device or a check valve on the main or a pressure reducing valve ...you need a Domestic extrol tank. The water has no where to go, that's where the weeping T&P valves, the premature tank failures enter into play. In Most well systems the well holding/expantion tank will do the job fine.kpc

Jason Roberts

If I understand correctly, the Domestic hot water (DHW) heated water expands and pushes the expanded water back out to the main supply from the city line?

kevin coppinger_4

not if there is.........

a check valve...and most towns and cities require there to be one of some type to protect the water supply from contamination.

Jason Roberts

Check Valve?

the Domestic water heater is directly connected to the potable system, it is not isolated, it provides hot water for bathing, drinking, washing etc. Where or why would there be a check valve?

kevin coppinger_4

right after the...

water meter coming into the house for backflow purposes as per most every water dept.code. Usually a Watts#7 or a 909.

Jason Roberts

Still not clear ?

Why the DWH doesn't have an expansion tank? I understand now that the water meter has a backflow valve to prevent return flow contamination.

Jason Roberts

Water Tank absorbs the expansion?

My understanding is water expand 4.3% when heated from 40 degree to 212 degrees. So roughly it would expand say 2% to get to 140 degrees and a 60 gallon tank would have to expand 1.2 gallons.Does the tank absorb this expansion?

chuck shaw

the domestic

hot water, would only require one, IF you have a backflow prevention device on your city supplied water. Either as part of the meter itself, or a seperate device. If you have a private well, it is probally not necessary. If you have an older home with an older water meter, this will allow water to pass back through the meter into the city system, therefor you would not need one. Not all cities and towns have the backflow prevention requirement.

Chuck Shaw

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

Jack_23

No the tank does not absorb

the expansion. Frequently expansion can just be pushed back out the system. If however you have a backflow preventer on your CWS or just a check valve on the CWS to the HW tank you will see the weeping PRV and it may require the additon of and expansion tank