Parallel or Series water heaters?

Timco

I can't remember the reasons to either parallel or series pipe two 40-gal water heaters. I have sen them in series and in parallel with a pyramid-type piping method. Water pressure is great, incoming water temp is mid-40's. House is all pex. Cust has 2 adults and 1 child showering now, and one on the way.  My 4-plex is series, and 7 total tenants with no complaint ever.



TIA,  Tim

JStar

I like...

Parallel piping, just so if one leaks, I can isolate it and keep the others going. I guess the advantage of series piping is that they don't all need to fire up to make enough hot water. The first in line will stay on the longest.

Big Ed_4

Twin Tanks

Twin tanks in series for hotter water . Using them to step up temperature of the water.… You may need for an industrial or manufacture application ...



Twin them in parallel in a residential application for larger quantity of domestic hot water .…



You may be looking for the hotter water but add a mixing valve for residential use

eluv8

twin hot water heaters

Series: When having a building load that varies and you want to maintain a constant water temperature. The first tank acts as a pre-heat tank to the second tank = less mixing stable temperatures and larger storage capacity.  Another variation with higher temperature loads (Only seen once) have the first tank at 120 and the second tank at 160 utilizing two seperate boilers one condensing the other non-condensing. Not a bad system when you think about it. Efficiency and redundancy. Piped either way the water heaters or boilers operate in a more staged arrangement with most of the load going to the first boiler/water heater in the system. Difficult to isolate tanks individually.



Parallel: Lots of hot water Fast. All water heaters in system operate independently of each other however operate as if they were one single larger water heater. They all go cold at the same time and get hot the same time. Duty cycle is similar for each water heater.



Hope this helps. I like to pipe in series simply for the potential efficiency and constant temperature benefits.