Why has filtering become very slow (over 30 minutes)?

There are several potential reasons for the issue you are experiencing:

First, it is possible that the filters have reached the end of their useful life cycle. Over time, filters can become less effective and may need to be replaced to ensure optimal performance. Additionally, the machine or the reverse osmosis (RO) filter could be clogged. This clogging may result from the accumulation of waste water scale deposits or due to the presence of extremely hard water, which can lead to mineral build-up that hinders the filtration process.

Another possibility is that you might be dealing with a defective filter. Filters can sometimes malfunction, which can also contribute to slow filtering times. To address these issues and find more detailed guidance, please refer to the following link for assistance: Why did the filtering time increase to over 20 minutes after I replaced the filter(s)?0 minutes?