A filter system is provided with a housing provided with a cover. The housing has a raw liquid inlet, a clean liquid outlet, and a liquid drain. A filter element is provided that separates a raw side from a clean side. A slide valve with a valve rod and a sealing head is provided, wherein the sealing head is arranged such that the liquid drain of the housing is closable but openable. A coupling is arranged between the sealing head and the valve rod, providing an axial securing action of the valve rod at the sealing head and a radial securing action, separate from the axial securing action, of the valve rod at the sealing head. A slide valve for such a filter system as well as a sealing head and a valve rod for such a slide valve are provided.

A removable filter cartridge includes a filter housing containing a filter for filtering liquid and a sealing valve assembly coupled to the filter housing and for removably coupling the filter cartridge to a filter head. The sealing valve assembly include an inlet passageway and an outlet passageway. The sealing valve also including an inlet sealing valve that blocks the inlet passageway and an outlet sealing valve that blocks the outlet passageway while the filter cartridge is uncoupled from the filter head. A method of retrofitting a filter housing includes removing the filter housing from a filter head, coupling a sealing valve assembly to the removable filter to form a removable filter cartridge, and coupling the removable filter cartridge to the filter head.

A method of detecting clogging of a fluid filter is disclosed. The method includes measuring, at successive sampling instants, the pressure difference ΔP from upstream to downstream across the filter, calculating the first time derivative {ΔP}′ of the pressure difference ΔP at different instants, and then sending a clogging signal S.sub.C representative of the filter being clogged when the first derivative {ΔP}′ is equal to zero.

A method of detecting clogging of a fluid filter is disclosed. The method includes measuring, at successive sampling instants, the pressure difference ΔP from upstream to downstream across the filter, calculating the first time derivative {ΔP}′ of the pressure difference ΔP at different instants, and then sending a clogging signal S.sub.C representative of the filter being clogged when the first derivative {ΔP}′ is equal to zero.

A method of detecting clogging of a fluid filter is disclosed. The method includes measuring, at successive sampling instants, the pressure difference ΔP from upstream to downstream across the filter, calculating the first time derivative {ΔP}′ of the pressure difference ΔP at different instants, and then sending a clogging signal S.sub.C representative of the filter being clogged when the first derivative {ΔP}′ is equal to zero.

A hollow filter element of a fluid filter has a filter element-associated retention/carrier device of a retention/carrier system retaining the filter element in a first housing section of a filter housing during installation/removal in or from a second housing section by rotation and/or insertion movement. The filter element-associated retention/carrier device has a retention/carrier part extending radially and circumferentially and has through holes adjacent thereto extending circumferentially so as to enable a filter housing-associated retention/carrier part of the retention/carrier system to pass through axially. This retention/carrier part has a tensile face extending circumferentially and radially on a side facing away from an end face of the filter element facing the first housing section. This retention/carrier part has a rear side in circumferential direction. A space axially adjacent to the tensile face is connected on the rear side to a through hole for guiding through the filter housing-associated retention/carrier part.

A hollow filter element of a fluid filter has a filter element-associated retention/carrier device of a retention/carrier system retaining the filter element in a first housing section of a filter housing during installation/removal in or from a second housing section by rotation and/or insertion movement. The filter element-associated retention/carrier device has a retention/carrier part extending radially and circumferentially and has through holes adjacent thereto extending circumferentially so as to enable a filter housing-associated retention/carrier part of the retention/carrier system to pass through axially. This retention/carrier part has a tensile face extending circumferentially and radially on a side facing away from an end face of the filter element facing the first housing section. This retention/carrier part has a rear side in circumferential direction. A space axially adjacent to the tensile face is connected on the rear side to a through hole for guiding through the filter housing-associated retention/carrier part.

An apparatus for filtering water has a valve head and a filtration/purification canister removably mountable thereon. Connecting the canister to the valve head automatically opens a check valve in the valve head to permit water to flow from the valve head into and through the canister, and then back to and through the valve head to an outlet port. Disconnecting the canister from the valve head automatically closes the check valve, stopping the flow of water. A bypass valve is provided in the valve head to permit a sanitizing solution to flow through the valve head and along the lines of the water distribution system to sanitize the system, while bypassing the canister. The outlet port may be directly connected to an appliance that uses water, to eliminate possible contamination that may occur when water is brought indirectly from the outlet port to the appliance instead.

An apparatus for filtering water has a valve head and a filtration/purification canister removably mountable thereon. Connecting the canister to the valve head automatically opens a check valve in the valve head to permit water to flow from the valve head into and through the canister, and then back to and through the valve head to an outlet port. Disconnecting the canister from the valve head automatically closes the check valve, stopping the flow of water. A bypass valve is provided in the valve head to permit a sanitizing solution to flow through the valve head and along the lines of the water distribution system to sanitize the system, while bypassing the canister. The outlet port may be directly connected to an appliance that uses water, to eliminate possible contamination that may occur when water is brought indirectly from the outlet port to the appliance instead.

An apparatus for filtering water has a valve head and a filtration/purification canister removably mountable thereon. Connecting the canister to the valve head automatically opens a check valve in the valve head to permit water to flow from the valve head into and through the canister, and then back to and through the valve head to an outlet port. Disconnecting the canister from the valve head automatically closes the check valve, stopping the flow of water. A bypass valve is provided in the valve head to permit a sanitizing solution to flow through the valve head and along the lines of the water distribution system to sanitize the system, while bypassing the canister. The outlet port may be directly connected to an appliance that uses water, to eliminate possible contamination that may occur when water is brought indirectly from the outlet port to the appliance instead.