I am in the process of initiating water temp testing at our farm facility. All of our heaters are undercounter water heaters that are cold fed. I know they have a small interanl tank approx 10 litres, but should we be testing hot and cold temps or just cold due to the cold water feed nature of the equipment. The max hot water range for the equipment is 54 degrees

Advice would be gratefully recieved

Morning!

First of all...legionella risk assessments can look simple (and often are!) but can sometimes be complex because of other factors. We're looking at one part at the end of a larger system here only.

However, with that caveat firmly in mind, the purpose of doing testing is to check that risk conditions for legionella growth don't exist - so in this case aiming to keep water below 20C or above 50C.

If the unit is, by design, warming and then holding the water then failures might foreseeably lead to temps in the 'danger' zone within the storage area. If there are outlets off this heater and associated pipework then what you're monitoring is whether there is any failure at this point in the system. So cold temps to check both this range of pipework and associated feed...and hot to check that the heater is heating sufficiently.

Given the volume of the unit I wouldn't be too worried about reaching 60. Small units can be 'fun' to do temp checks on as sometimes running them for a minute at the wrong time can drain the last dregs of hot water out and give you a potential false non-compliant result. ;)