A filter module comprising: - a filter housing having a filter chamber, the filter housing comprising: ∘ a first housing member; ∘ a second housing member configured to be coupled to the first housing member and having a connection portion with an inner side and an outer side that is configured to face away from the filter chamber, the outer side having a filter inlet and a filter outlet; and ∘ a filter valve coupled to at least one of the filter inlet and the filter outlet, the filter valve biased toward a closed configuration in which fluid communication is substantially prevented through the filter valve; and - a filter configured to be disposed in the filter chamber; - a first filter cap configured to be disposed between the connection portion of the second housing member and the filter to maintain the filter valve in the open position such that fluid communication is permitted through the filter valve between the filter chamber and at least one of the filter inlet and the filter outlet, characterized in that an outer side of the filter cap includes a recess with a first transverse dimension and at least one second transverse dimension that is smaller than said first transverse dimension and closer to the end of an inner projection than is said first transverse dimension and in that it includes a plurality of ridges extending radially inward into said recess to define a second transverse dimension being is larger than a bottom cylindrical portion of a valve body of the filter valve, but is smaller than a maximum transverse dimension of a plunger, such that a lower cylindrical portion of the valve body can extend into the recess beyond upper ends of ridges and but lateral projections cannot extend beyond upper ends of the ridges, to thereby ensure that, if filter valve is fully seated in the recess and projection is fully seated in a recess of the second housing member, a plunger is moved to and/or maintained in its open position to permit liquid to flow through channel of the plunger and through valve openings and guide slots of the valve body. - a filter housing having a filter chamber, the filter housing comprising: ∘ a first housing member; ∘ a second housing member configured to be coupled to the first housing member and having a connection portion with an inner side and an outer side that is configured to face away from the filter chamber, the outer side having a filter inlet and a filter outlet; and ∘ a filter valve coupled to at least one of the filter inlet and the filter outlet, the filter valve biased toward a closed configuration in which fluid communication is substantially prevented through the filter valve; and ∘ a first housing member; ∘ a second housing member configured to be coupled to the first housing member and having a connection portion with an inner side and an outer side that is configured to face away from the filter chamber, the outer side having a filter inlet and a filter outlet; and ∘ a filter valve coupled to at least one of the filter inlet and the filter outlet, the filter valve biased toward a closed configuration in which fluid communication is substantially prevented through the filter valve; and - a filter configured to be disposed in the filter chamber; - a first filter cap configured to be disposed between the connection portion of the second housing member and the filter to maintain the filter valve in the open position such that fluid communication is permitted through the filter valve between the filter chamber and at least one of the filter inlet and the filter outlet,