megaflo tanks

[Belle427]

i have been looking at a problem with a pair of megaflo tanks that are coupled together feeding a small commercial kitchen,the hot water is inconsistent,there are 3 immersions per tank,which i have tested,and i have checked out the thermostats and replaced 2 faulty units
in this arrangement does the water pull from each tank equally when the taps are switched on? it would seem when the water starts to go cold that one of the tanks still has its cylinder full of hot water as the stats are maintaining roughly 65 degrees,and the outlet pipe on the top is hot,the only problem i can possibly see is the gate valve on the top of the tank playing up,the pipes are lagged so i didnt disturb this to feel the pipe each side of the gate valve
any thoughts please,they are the direct style tanks

 

[ACOperson]

What size are the pipes coming off the top of the units and where do they converge?

Its not common practise to put gate valves on mains pressure water by the way! Who installed these cylinders?

 

[Belle427]

thanks,they look like 22mm outlets,the tanks are side by side and are coupled together above,there is one supply pipe to the hot water system and both tanks have gate valves in their lines,no idea who installed,but they have been working for years

 

[ACOperson]

Usually when there are 2 in series, they will rise from cylinders in 22mm, then when they meet in the middle of 2 units, size increases to 28mm. Otherwise whats the point of having 2?

Yes, one of those gate valves may be to blame. Or, could be a problem with one of the cylinders. I'm not all that experienced on Megaflows but think there are sometimes problems with the internal air gap & pressure reducing valves.