OK, here is the situation:

I recently bought a dishwasher that has a shorter water hose than required. So I bought this inlet hose and connected the two hoses using this inlet connector.

For water supply I used a self cutting tap.

The problem is, when dishwasher tap is open (dishwasher not working), and I open the main drinking water tap, my water has strange smell and taste. (This is not the case when the dishwasher tap is closed or the dishwasher hose is connected to tap without extension).

The only cause I could conclude from this is that the water flows back from inlet hose into the drinking tap, giving it the odor and taste. (although I can't tell the inlet hose smells by sniffing!)

Is there anything I can do to prevent this? I already tried returning the inlet hose and trying another one (maybe that particular one had issue) -- but no success.

update:

Today I came up across this shower check valve. Do you guys think this can prevent the backflow of water if I install it on my dishwasher tap?