When the backup valve is stuck on only allowing to use T3 water, this has a few effects.

Location

The valve is located on a different spot for V1.X systems and V2.X systems. Please check the version of the Hydraloop in the hdm on the "Device" tab to confirm which one is applicable.

Location of V1.X systems

On the V1.X systems, the backup water valve is located directly under the transparent T4 tank. Two valves are connected together here. But the valve directly under the transparent T4 tank is the backup water valve.

Location of V2.X systems

The location of the backup water valve is right behind the distribution pump. The valve has a blue casing. Please note that other valves have the same casing. But this one is specifically connected to the black 'distribution pump'. See image.

Causes

IO-board (water) damage

Problem
The IO-board that controls the Hydraloop can also be damaged. Often the damage manifests as valves or other components constantly being powered. Or not powering at all. The damage could be clearly visible (see below image of clear calcium marks from dried up water). But often it is not that easy to see.

Solution
Replacing the IO-board is the only thing that would solve this problem.

Component failure

Problem
Another possible cause is component failure. The component failure could be:

The valve can also be stuck in an in-between position. See below photos of this wrong case.

Solution
WARNING: Make sure the new valve is installed properly. As the valve has 3 holes, it is possible to install the valve the wrong way around. Use the orientation of the previously installed valve as reference.

Replacing the valve would be the only solution. To replace the valve follow these steps:

Testing
After replacing the valve, please test if the replacement was successful. The best way to currently test the valve is by: