Help needed with General Ecology filter in Kenya

[becausewecan]

Hello all, we are hoping we can get other overlander's experiences and advice on our current filter system...

We are currently in Nairobi, having been on the road for nearly five months. Before leaving we installed a General Ecology Seagull filter into our 4x4, purchasing two catridges (one in the filter, one for a spare). The retailer we bought it off suggested we would not need the spare, but we just wanted to be on the safe side. Our first catridge stopped working in Sudan, so we put the spare in whilst in Khartoum. The second catridge is now on its way out, and we are wondering what on earth we are either doing wrong or whether the filter is simply not up to the job (though all other threads on the Hubb seem to suggest everybody but us is happy with it?) Two other overlanders we have met on the road have the same system and are happy with it, although both are rarely using it whereas we have been putting all of our drinking water through.

We have contacted the retailer we bought it off, and he implied it was our own DIY installation or the pump that was at fault. But we have put in a Shurflo pump at a higher spec then recommended, and have tested it by removing the filter and the pressure is still really strong. We have only put in tap water to our tank. We are now unsure if we should change systems (as we haven't been able to find replacement catridges in Kenya), which will cost us big, or get more catridges sent (which will again cost and who knows how long they will last). We are reluctant to switch to bottled water or use chemicals...

Any ideas would be greatly appreciated?

Mark and Allison