Couple of months ago I upgraded myself with 8mm silicone hose and the ECs couplings. Since I have had constant leaks in my vacuum. I haven't bothered too much and have run with the pump on. Last month I decided to examine where the leak was. First I checked the couplings attached directly on the pump. All good. Then attached the hose with couplings in each end. Leakage! 
First I tried to replace the tape on the couplings, still leaking. Then I bought some specific thread sealant, still leaking. Then on top the hose I put specific hose clamps. Still leaking. Is the conclusion that the couplings themselves are leaking or am I missing something obvious here? 

Which couplings are you using, the quick disconnect ones? These ones have an o-ring inside the female connector that is very easy to tear if you dont connect the two together straight enough. Have a look inside and see if you can see any damage on that o-ring.