How do I repair a bath mixer tap when the water is running half into the bath & only half is going up to the shower head? The control for the water to go up the shower head is by pressing down a ring on the bath tap just at the bottom of the hose leading to the shower head.

Most likely, the diverter on top of the spout is malfunctioning. You have two choices:

1. Rebuild the existing spout/diverter
2. Install new spout with diverter

We usually replace spout since it is hard to get replacement parts for diverter. Spouts are not so expensive and it is a sure fix.

Milo, you got this right for 99.9% of this complaint. However, I am hoping TW can post a picture of her valve, I think we may have something different going on here, maybe. Bob