Forum Title: How many degrees does hot water temp drop through pex?
If the gas tankless water heater is set at 125 degrees and the hot water runs through 200' of 3/4" pex and 10' of 1/2" pex before it gets to the faucet, what temperature would you expect at the faucet? The temperature in the attic where the hot pex line is routed is 80 degrees. There are some 1/2" branches that route to other faucets along the way. How long would it take for max temp hot water to get to the faucet from the tankless? Would I expect hot water within a few seconds at the faucet if there is a recirculation line/pump installed? Thanks in advance
Category: Plumber Post By: STACY DOUGLAS (Tustin, CA), 08/27/2017

if you have a circ line like this then the main will be within a degree or 2 of what your setting at the heater is the branch going to the fixture will take a few seconds to get hot if you want instantaneous hot water go with the under the counter pump

- TERRY NGUYEN (Rock Hill, SC), 09/06/2017

and the faucet says it's a 1.2gpm max flow rate.

- WILMA VEGA (Kansas City, KS), 09/08/2017

Quote: Originally Posted by frodo if you have a circ line like thisAttachment 14789 then the main will be within a degree or 2 of what your setting at the heater is the branch going to the fixture will take a few seconds to get hot if you want instantaneous hot water go with the under the counter pump That's what I suspected, I for sure have a problem somewhere. It's taking 10-15 seconds for it to get lukewarm and then it slowly warms up from there. It takes a minute to get semi hot and then it's still 15 degrees below the tankless output temp. The output temp at the water heater was supposedly 127 degrees when I tested today. This is new construction, brand new everything. Could bad cartridges inside single thermostatic handle shower valves be causing some sort of crossover? Even if there was 200ft of 3/4 pex with a 10' branch to the faucet, it still should not take very long with a proper recirculation system correct?

- CATHERINE CARTER (Blacksburg, VA), 09/28/2017

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