ᐅ Pipe vent / backflow preventer leaking – What for?

Hello everyone,

A few weeks ago, we moved into our new house and in the kitchen, at the cold water connection (and only there), we have the adapter shown in the attachment. I believe it is a pipe vent with a backflow preventer.

I connected a Y-connector behind it to attach the dishwasher and a direct water supply for our side-by-side refrigerator.

My problem is that this adapter does not seal properly; I have tried everything. Without this adapter, everything stays dry.

Can someone tell me what it is used for and whether it is absolutely necessary to keep it installed?

Thanks and best regards

As far as I know, DIN 1988.

I believe this device creates an air gap when no water is flowing. This is necessary to prevent bacteria buildup or contaminants from flowing back into the water supply. I had to retrofit something like this for faucets that are not used continuously.