filters this may result in highly efficient or thorough filtration if all filter cartridges 26 are of similar filtration characteristics alternatively filter cartridges 26 may have different filtration characteristics illustratively different contaminants could be trapped by different filter cartridges 26 use of four different filter cartridges could be exploited to eliminate many different contaminants which could be present in unfiltered water passing through the domestic plumbing system passages formed in bottom 28 of canister 20 are illustrated in the plan view of fig4 water discharged from port 64 fills chamber 22a and open center 74 of filter cartridge 26a this water is conducted by a canister internal passage 76 to chamber 22b water will fill open center 78 of filter cartridge 26b then pass through a canister internal passage 80 to chamber 22c water will finally pass through a canister internal passage 82 to chamber 22d thus passages 76 80 82 each communicates between adjacent chambers 22a 22b 22c 22d transferring liquid in serial fashion from one chamber 22a 22b or 22c to subsequent chambers 22b 22c 22d water leaves chamber 22d through a port 94 of outlet 18 certain components of novel filter housing 10 have been omitted for clarity in the view of fig4 fig5 shows the components omitted from fig4 walls 24 and filter cartridges 26 are omitted from fig5 for clarity pick up tubes 44 are seen to depend from bottom surface 38 there being one pick up tube 44 for each chamber 22 see fig1 of canister 20 fig5 also shows internal passages formed in cap 12 and in bottom 28 of canister 20 a first cap internal passage 86 conducts incoming water into the first chamber 22a see fig4 a second cap internal passage 88 comprises a portion of the flushing circuit.