I installed a Seagull filter on our boat a few seasons ago (pricey - but very effective). We have a foot pump drawing water from the tanks to the galley sink. I bought a 3-way valve from US Plastics and plumbed the filter so that it could be set to the pressure side, or the manual foot pump side.
The rather large charcoal filter creates quite a bit of resistance to the water pressure. The pressure pump handles the filter nicely, the foot pump side has a very much reduced flow rate even with energetic pumping. Even at that I find it useful, allowing water to be pumped from the tank even if a pressurized side failure, or electrical fault occurs. It is very workable, the foot pump diaphragm does not lock - but expect flow to be restricted.