thermal expansion

[rstotz]

gentlemen, small time old town, big time problem. town installed new water meters with check valves in all houses. Houses without expansion tanks are experiencing pipe failures. Exactly how much water is displaced (pushed backwards} in piping without check valves during a normal heating cycle of a hot water heater. Will someone please punch the numbers and have an easy answer that borough councle members can understand. Here is the info I can give you. supply line 3/4 id house line 1/2id copper normal system pressure is 60 psi. supply water temperature varies from summer to winter. do not take temperature/pressure relief valves on water heaters in to consideration. I really think someone is going to put ther water tank into orbit sooner or later. thanks, Richard

 

[IRstuff]

If these are old systems, the most likely problem is that the new meters are now supplying the CORRECT water pressure, whereas, before, the old meters were restricting the water pressure from reaching the old pipes.

TTFN

 

[JimCasey]

v water at 20C s 1,001797 cc/g
v water at 60C is 1.017089 cc/g
that's a 1 1/2% volumetric change

If you use 40 gallons for a bath, and the water heater heats 60F water up to 140F, the expansion is 0.6 gallons.

If you don't let it expand, according to table 6.1.8 of page 6-10 of Mark's Handbook the thermal expansion coefficient of water would be 4.26 x 10-5/psi. It will raise the pressure in the system by up to 358 psi.

You should be popping the safety valves on water heaters in the houses without expansion tanks.

 

[electricpete]

Do you want to know how much water is displaced, or how much will pressure go up for trapped volume during thermal expansion.

If the latter, I would think we could calculate a pressure increase per temperature for increase based on ratio of temperature-density coefficient and pressure-density coefficient.

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[rstotz]

both water displacement and pressure increase would be nice to know. displacement will show that no water softner water will make it back to the main in the street. Borough is concerned with cross contamination of city water. Pressure will prove that the borough officials did not do there homework by puting check valves in old water systems that didn't require expansion tanks at the time the code was written. It was only after faucets starting leaking, waterheaters split and fitting started to seep that the borough sent follow up letters stating there could be possible expansion problems. Guess who gets stuck with the bill to fix? Thanks for answers Richard

 

[25362]

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