When this happened, I assume that the bathroom was in first fix stage. The shower valve (blue Grohe box) was mounted/connected but the actual valve/chrome controls where not currently connected.
I fit these. Following the install instructions, once, you’ve connected the pipework to the box, you need to install a plastic dummy test valve.
Then you turn the water on to ensure no leaks and flow from the outlets.
If you were in first fix (before tiling), it’s likely that once tested, the outlet connections were capped during tiling.
If the above is correct, I then reckon the dummy valve wasn’t removed and the inlet bungs installed in the shower box. You install these bungs (one for hot and one for cold). Once bungs are installed, you reinsert the dummy valve and close up the box. This allows the water to stay turned on until tiling complete/valve installation.
However, if after testing, the dummy removal/bung install wasn’t completed, the valve box provides a link between the hot and cold feeds.
I fit these. Following the install instructions, once, you’ve connected the pipework to the box, you need to install a plastic dummy test valve.
Then you turn the water on to ensure no leaks and flow from the outlets.
If you were in first fix (before tiling), it’s likely that once tested, the outlet connections were capped during tiling.
If the above is correct, I then reckon the dummy valve wasn’t removed and the inlet bungs installed in the shower box. You install these bungs (one for hot and one for cold). Once bungs are installed, you reinsert the dummy valve and close up the box. This allows the water to stay turned on until tiling complete/valve installation.
However, if after testing, the dummy removal/bung install wasn’t completed, the valve box provides a link between the hot and cold feeds.
