One. What are the common causes of water leakage in newly installed complete bathroom fixtures?
In cases of overall bathroom water leakage, this typically occurs due to failure of the waterproof strip. If the waterproof strip is confirmed to be damaged, you can replace it with a high-quality waterproof strip and then use a silicone gun to apply silicone to the inner edge of the strip, effectively sealing the leak.

If water has leaked onto the roof of the lower floor, this indicates a problem with the waterproofing in the bathroom. It is necessary to hire a professional electrician to address the issue. This involves removing the existing tiles, applying a second layer of waterproofing, and then installing new tiles.
Two. How to solve overall bathroom leakage issues
First, we must pay attention to the waterproof seals and waterproof substrates of the entire bathroom. This is essential for ensuring that the entire bathroom does not leak, as the waterproof seals of the entire bathroom should ideally be a continuous strip. If there are joints, pay attention to whether any parts are disconnected. Some entire bathroom waterproof seals are poorly processed, and some even have glass directly contacting stone, which can lead to glass breakage and leakage.
Secondly, it is essential to ensure that the entire bathroom floor drains are smooth, easy to clean, and effectively block water, otherwise the entire bathroom will become a "bathtub." Regarding the issue of water accumulation in the entire bathroom: create drainage channels on the entire bathroom floor, with drainage channels around the edges and a central water guide channel. When water falls onto the floor, it will be directed into the surrounding channels. Although it cannot completely eliminate water immediately, it will prevent water from accumulating.