Dosing Pump Issue

Hi

Based in the UK I recently (Saturday 2nd December 2017) purchased a 4 channel SA Doser 2.1 from H2O aquatics in Brentwood and am so far a little disappointed.

Pumps 3 & 4 both appear to jam fairly frequently when dosing / calibrating.

I have taken the blue cover plates off, wiped over the inside and the rollers, carefully re-seated all parts and for a while the pumps behave themselves but then will jam !!

Daily dose from them is 40ml and I have been calibrating every night this week - on all occasions jamming has occurred for both.

Pumps 1 & 2 are fine.

Anything else I can try ?

Thanks

Andrew