I have a Gardiner's back pack it's about 3 years old I have put many hundreds of ltrs of hypo through it , I always wash it through after , it's still working fine , they are cheap enough to replace every year if you have to they should pay for themselves with one or two jobs , so I feel it's good value for money , I know Alex won't warranty it if hypo is used but if it went wrong I would just get another one