I have two hot water tanks connected in parallel with a 1 inch hot water pipe. The tanks are 75 ft apart. The cold water feed is also a 1 inch pipe. The tank thermostats are set at
145 F. There are 14 faucets getting hot water from these tanks. There is no shut off valve between the tanks hot water pipe. We will call the front and the rear hot water tanks.
The problem is if I open a hot water faucet near the rear water tank (approx 15 ft), it would take about 5 minutes to get hot water unless I open another hot water faucet near the 1st faucet. It appears the hot water travels from the front tank first (75 ft away) before getting water from the rear tank. I also noticed as the front tank hot water gets close to the rear facet, the pipe from the rear tank is getting hotter. I believe the hot water is coming from both tanks after the water reaches max temp.
Is the symptom experienced due to the property of cold and hot water traveling into a pipe? I know how to fix the problem but I would like to understand what is happening with this plumbing set up. Thank you.

Pierre

Hello pierre, Do you have check valves on both cold water supply's to the two water heaters? No recirc pump? It sounds like the front tank is pushing water back to the rear tank that would explain why you get cold water when you turn the back lav. That's why there should be checkvalves at the cold water supply's at both water heaters. Check the valve to the rear water heater to make sure that the valve is fully open, you can turn the front water heater valve off to check what the pressure is like on the rear one. Hope this helps good luck.----Zeke

Zeke,

I thank you for your information. There is a check valve on each cold water supply's of the water tanks. The valve at the rear of each water heater is fully open. If I shut the front hot water valve, the hot water comes from the rear tank with about the same pressure. I have observed when the hot water pipe has removed the cold water (coming from the front hot tank) and the hot water is near the rear sink, the rear hot water tank pipe starts drawing hot water from it. The rear hot water tank pipe gets hot immediately.
Pierre

Hello C. pierre, 1. what type of faucet do have on lavs? 2. do you have mixing valves at the waters? 3. does the main water supply to the building come in from the front water heater side or the rear water heater side? I'm wondering if the supply is closer to the front water heater, that when you turn on the faucet next to the rear, that the hot water is being drawn from the front water heater first for some reason. Are checkvalves spring or swing type ? That might be where the problem is. Thanks Zeke