Condensation around water tank

Doop

Just looking to see if anyone could provide some insight here. We've had an issue in an attic void with water discovered on the floor, initially we suspected it was a roof issue, so we had roofers out who repaired a leak. We've since had the water reoccurring. The attic has a couple or cold water tanks. The attic is fully insulated on the internal side of the slope of the roof. The tanks are not insulated. The tanks have been here for years with no issues, suddenly the first tank is forming alot of condensation around it and also the pipe working running to it. The pipework is insulated. The neighboring tanks have no condensation atall... so why only this one? There is a tray under the tank and sure enough there's a bit of water in it which looks to be from the condensation.

We're a bit baffled by it. You can see in the photo the tank on the right has lots of condensation and the one on the left has none. There are more tanks out of shot again with no condensation.

10-10-20

Hi. Where does the cold water riser (incoming water) connect to? Is it one tank or both? If it's just into one tank, is there an interconnecting pipe between each tank?

If it's just feeding into one tank (the right one in the photo) then it's simply that the incoming water is making the right tank colder than the left and that's the cause of the temperature difference between both.

But at the end of the day you need to ensure that the attic is very well ventilated. Are there indications of moisture on the roof felt during very cold periods?

Wearb

If its been there without issues and nothing has changed (attic insulation-wise), then it can be a sign of continuous water replacement. Perhaps due to a faulty ball cock, tap left on somewhere or a leak.