referring firstly to fig1 to 3 , a separator device for separating particles from suspension in a fluid is indicated generally at 10 . a housing 12 is provided , comprising of a body portion 14 and a removable closure portion 16 . the body portion is substantially a cylindrical shell open at the upper end , that is , the body portion 14 comprises a floor and a wall 17 . the upper end of the wall 17 of the body portion 14 is formed with a male thread 18 and , directly below the male thread , a circumferential rim 20 . the closure portion 16 is in the form of a screw - on cap comprising a circular planar roof 26 and a circumferential wall 28 extending below the edge of the roof . a thread 22 is formed on the interior surface of the wall 28 , for co - operating with the male thread 18 at the upper end of the wall 17 of the housing body portion 14 . a plurality of recesses 24 are provided spaced uniformly around the outside of the wall 28 of the closure portion 16 in order to assist a user in gripping the closure portion 16 to effect closure and removal . a recess 30 is provided around the edge of the underside of the roof 26 of the closure portion 16 . a rubber o - ring 32 sits within the recess 30 , around half of the height of the o - ring 32 extending below the underside of the roof 26 . when the closure portion 16 is screwed onto the body portion 14 of the housing 12 , the o - ring 32 is compressed between the roof 26 of the closure portion 16 and the upper edge of the wall 17 of the housing body portion 14 , forming a watertight seal . an inlet and an outlet are provided as first and second hollow cylindrical sockets 96 in the wall 17 of the housing body 14 , each extending perpendicular to the same tangent of the cylindrical body , that is , the sockets extend outwardly from the wall of the housing 14 and are parallel to each other on a diameter of the housing 12 . john guest speedfit ® connectors 98 are provided within the sockets 96 , allowing easy fitting to a heating circuit . the parallel inlet and outlet sockets 96 on the same diameter enable easy fitting to a heating circuit , since the inlet and outlet will be in the same straight pipe line when the device is installed . deflectors 100 , best shown in fig2 , are provided within each of the sockets 96 in the cylindrical housing 12 . the deflectors 100 block a portion of each socket 96 , directing the flow on the inlet to one side and resulting in a swirling flow within the housing 12 . the edges of the deflectors 100 are at an angle of around 10 ° from the vertical , so as to divert water slightly vertically as well as horizontally . providing deflectors 100 in both sockets 96 allows either to be used as the inlet . a bleed valve 102 is provided through the center of the screw - on cap 16 and is screwed into a plug 50 within the housing 12 . the bleed valve includes a head portion 106 and a body portion 108 , the head portion 106 being of greater diameter than the body portion 108 , so that the body portion 108 but not the head portion 106 will fit through a circular aperture in the center of the roof 26 of the closure portion 16 of the housing 12 . a passage 120 is provided through the center of the head and body portions 106 , 108 . the head portion 106 is provided with an external screw thread , and a screw - on cap 104 closes the bleed valve , sealed by an o - ring arrangement . a drain valve 116 comprising of a screw - in plug with seal is provided in the floor of the housing body 14 . in use , the separator device 10 is isolated from the heating circuit , and the bleed valve 102 and drain valve 116 are opened to drain fluid from the housing 12 . the drain valve 116 is then closed , and the system can be dosed with a corrosion inhibitor via the bleed valve 102 . a supply line can be secured onto the thread of the head portion . the separator device 10 is then reconnected to the heating circuit , air being forced out of the bleed valve 102 . when all the air has been removed the bleed valve 102 is closed , and the system refilled and / or re - pressurized as necessary . referring now to fig4 - 8 , an insert 34 is removably contained within the housing 12 . the insert comprises a central section 36 formed as a hollow cylinder , a first separation chamber 38 at an upper end of the insert and a second separation chamber 40 at a lower end of the insert , as viewed and installed in the housing . the upper and lower separation chambers 38 , 40 are substantially cylindrical and share a central axis with the central section 36 . the upper and lower separation chambers 38 , 40 are sized to almost completely extend to the full interior diameter of the housing body 14 . the hollow cylindrical central section 36 has a curved wall which is approximately 0 . 65 mm thick . four equally spaced reinforcing ribs 37 are provided , each around the circumference of the outer surface of the cylindrical central section 36 . four equally spaced reinforcing spines 33 are provided perpendicular to the ribs 37 . the ribs 37 and spines 33 define rectangular panels 35 . a cylindrical magnet is provided inside the hollow central section 36 of the insert 34 , the central section forming a sheath around the magnet . in use , the magnet attracts ferrous particles which collect in the panels 35 on the outer surface of the central sheath section 36 of the insert 34 . when the heating system is serviced , the insert 34 may be removed from the housing 12 , and the magnet removed from within the central sheath section 36 . with the magnet removed , ferrous particles will easily fall away for disposal . the upper separation chamber 38 is formed as a cylindrical shell with an open top end , that is , a circular tray having a floor 44 and a single curved wall 46 . the floor 44 has a circular aperture at its center which has the same interior diameter as the hollow central section 36 of the sheath 34 . within the upper separation chamber 38 , protrusions 48 extend from the floor 44 , the protrusions 48 having a vertical extent matching the vertical extent of the wall 46 . the protrusions 48 form interior walls which define passageways within the upper separation chamber 38 . the arrangement of the protrusions 48 is best shown in fig6 . the arrangement is reflectively symmetrical about two orthogonal axes a - a , b - b . two protrusions of a first type 56 face each other . the protrusions of the first type 56 are formed of a curved wall 58 comprising substantially 90 ° of a circle arc , with a radius of curvature slightly smaller than the radius of the upper separation chamber 38 , and a straight wall 60 extending inwardly from the center of the curved wall 58 towards the center of the chamber 38 . approximately one third of the length of the straight wall 60 extends beyond a straight line c - c between the ends of the curved section 58 . the concave faces of the curved walls 58 face each other . the protrusions of the first type 56 are positioned with the straight wall 60 on a diameter b - b of the upper separation chamber 38 , and so that the curved wall 58 does not touch the wall 46 of the upper separation chamber 38 , enabling water to flow around all sides of the protrusions 56 . two protrusions of a second type 62 face each other at 90 ° to the protrusions of the first type 56 . the protrusions of the second type 62 each comprise a stem 66 extending from the wall 46 of the upper separation chamber 38 towards the center of the chamber 38 , and two hook - shaped walls 64 . the stem 66 widens as it approaches the center of the upper separation chamber 38 . the stem 66 meets the surface of the plug 50 , curving around the surface of the plug . the hook - shaped walls 64 extend from either side of the stem 66 where it meets the plug 50 , at an angle of around 55 ° from the stem , so that the hook - shaped walls 64 curve back towards the outside wall 46 of the upper separation chamber 38 . before the hook - shaped walls 64 meet the wall 46 of the upper separation chamber 38 , they curve around 90 ° in the direction away from the stem 66 , forming a hooked end . the extent of the hook after the 90 ° curve is substantially half of the extent of the hook before the curve . two straight protrusions 68 , having similar vertical extent to the above mentioned protrusions 56 , 62 and to the wall 46 of the upper separation chamber 38 , are disposed adjacent to the wall 46 on the diameter b - b of the upper separation chamber 38 , projecting inwardly towards the center of the upper separation chamber 38 . four slots 118 are provided in the floor 44 of the upper separation chamber 38 . the slots serve to guide a portion of the swirling flow of water within the housing 12 into the upper separation chamber 38 , without significantly reducing the overall flow rate in the heating circuit . the slots 118 spiral upwardly into the first separation chamber 38 , in opposing arcuate directions , and extend through the side wall 46 . that is , two spiral upwardly in one arcuate direction , and the other two in the opposing direction , for guiding flow into the upper separation chamber 38 irrespective of the direction of swirl within the housing 12 . the lower separation chamber 40 is formed as a tray 70 , best seen in fig7 , which is detachable from a lid 72 . the lid 72 is an integral part of the removable insert 34 . the tray 70 is toroidal with an inner wall 76 , an outer wall 78 and a floor 80 . the tray 70 has an outer diameter just less than the interior diameter of the housing body 14 and an inner diameter substantially matching the external diameter of the central section 36 of the removable insert 34 . a plurality of planar walls 82 extend from the tray floor 80 , each wall 82 joining the outer tray wall 78 to the inner tray wall 76 , and each having a vertical extent just less than the vertical extent of the tray walls 76 , 78 , so that water can flow over , but not under or around the planar walls 82 . the planar walls 82 are fourteen in number , and are spaced evenly around the toroidal tray 70 at sixteenths of its circumference , two sixteenths being without walls 82 , those two sixteenths being opposite each other and the arrangement of walls 82 being reflectively and rotationally symmetrical about a diameter d - d upon which the sixteenths without planar walls 82 lie . thus the planar walls 82 are arranged in two sections , each section having seven walls 82 . substantially cylindrical protrusions 84 extend from the tray floor 80 and are coincident with the planar walls 82 , so that that the cylindrical protrusions 84 extend through and above the substantially planar walls 82 . the planar walls 82 at the ends of the sections are coincident with two cylindrical protrusions 84 , as is every second wall 82 in each section , the remaining planar walls 82 being coincident with a single cylindrical protrusion 84 . where a planar wall 82 has a single cylindrical protrusion 84 , the cylindrical protrusion 84 is at the center of the wall 82 , equidistant from the inner and outer walls 76 , 78 of the toroidal tray . where a wall 82 has two cylindrical protrusions 84 , the distance between a first cylindrical protrusion and the outer tray wall 78 is equal to the distance between a second cylindrical protrusion and the inner tray wall 76 . each aforementioned distance is approximately one quarter of the distance between the inner and outer walls 76 , 78 . the lid 72 of the lower separation chamber 40 is formed as an annular roof 86 surrounding the central section 36 of the insert 34 , with a wall 88 extending below the edge of the roof 86 . the interior diameter of the lid 72 is substantially matching the exterior diameter of the tray 70 of the lower separation chamber so that the lid 72 fits over the tray 70 . apertures 89 are provided in the roof 86 of the lid 72 at either side of a radius , and are formed as two elongate rectangles , each with a longitudinal extent just less than the distance between the inner and outer sides of the annular roof 86 , and the longitudinal axes of each being parallel with each other . the two rectangular apertures 89 are together reflectively symmetrical about a radial axis halfway between the apertures . a flow guide 90 extends upwardly from the upper surface of the roof 86 of the lid 72 , on the radial axis of symmetry between the apertures , thus forming a wall between the apertures . the flow guide 90 becomes wider as it extends upwards , so that it forms an angled deflector adjacent to and overhanging each aperture . the flow guide 90 therefore deflects a portion of the swirling flow downwards into the lower separation chamber 40 , irrespective of the direction of swirl within the housing 12 . on the diameter d - d of the tray 70 which forms the space between the two sections of seven planar walls 82 , two cylindrical pins 92 are provided near the top of the outer wall 78 , extending outwardly from the outer wall 78 . co - operating slots 94 are provided in the walls 88 of the lid 72 extending vertically from the base of the lid wall and then laterally . in use , the tray 70 is slotted onto the lid 72 and then rotated to lock the tray 70 to the lid 72 , in the manner of a bayonet connector . referring now to fig9 to 14 , a fitment for fitting the separator device 10 in - line in a central heating circuit is shown generally at 130 . the fitment 130 comprises first and second sockets 132 for accepting the open ends of pipes , a screw compression fitting 134 of well - known design on each socket 132 for forming a sealed connection with the pipe ends , and first and second john guest ® speedfit ® connectors 136 , fluidly connected respectively to the first and second pipe sockets , for fitting to the speedfit ® connectors 98 in the inlet and outlet 96 on the housing 12 of the separator device 10 . a first valve 138 can be operated to break the fluid connection between the first pipe socket 132 and the first speedfit ® connection 136 , and a second valve 140 can be operated to break the fluid connection between the second pipe socket 132 and the second speedfit ® connection 136 . one of the two sockets 132 has a greater pipe receiving depth than the other , for example , twice the pipe receiving depth . plugs 142 are provided on the backs of the pipe sockets 132 . the plugs include a circular section 143 adjacent to the back of the pipe socket 132 , and a square dog section 145 at the end of each plug 142 . a recess 147 is provided around the curved surface of the circular section 143 , and an o - ring 149 fits within the recess , protruding beyond the curved surface . a spacer 144 is provided for fitting between the backs of the first and second pipe sockets 132 . the spacer 144 is sized to ensure that , when it is fitted , the speedfit ® connectors 136 on the fitment 130 are the same distance apart as the speedfit ® connectors 98 in the sockets 96 on the housing 12 of the separator device 10 . the spacer 144 is formed substantially as a cylinder . recesses 146 are provided on an outer wall 152 of the spacer 144 to provide torsional rigidity without increased mass . a socket 148 extends through the spacer from the top to the bottom , and is in the shape of a circle with two opposing truncated segments . at either end of the spacer 144 , the socket 148 has sections which are circular without truncated segments . the circular end sections of the socket are sized to receive the circular sections 143 of the plugs 142 . the circular sections 143 of the plugs 142 will not fit through the parts of the socket 148 having truncated segments , however the square sections 145 of the plugs 142 do fit into the truncated socket sections . when a plug 142 is inserted into a socket 148 , the square end dog section 145 of the plug 142 will be received into the portion of the socket 148 which has truncated segments . turning forces which act upon one of the compression fittings 134 will therefore be transmitted through the spacer to the other compression fitting 134 . by using two spanners , the net torque which is transferred to the inlet and outlet 96 of the separator device 10 is substantially reduced , limiting the possibility of damage . alternatively , the fitment 130 may be provided with a fitting jig 180 , as shown in fig1 . the fitting jig includes at least two apertures 182 to fit over the connectors 136 . the fitting jig ensures that the connectors 136 remain in line , whilst the separator device 10 is not attached . this eliminates any possibility of damaging the separator device 10 while fitting . the dog may have a different cross section if desired , such as a hexagon . when a plug 142 is inserted fully into a socket 148 , the o - ring 149 on the plug 142 acts to retain and align the plug 142 in the socket 148 , requiring a positive force for removal . in use , a section of the central heating flow or return pipe is removed . where some manipulation of the central heating pipe is possible , the fitment 130 may be installed without removing the spacer 144 . the socket 132 with greater pipe receiving depth is installed first , and is slid over the end of the pipe until the socket 132 with lesser pipe receiving depth can face the other open end of pipe . the fitment is then slid in the other direction , over the open pipe end . a fitment installed in this way is shown in fig1 , and with filter 10 fitted in fig1 . the spacer 144 may alternatively be removed entirely to allow fitting of the separator device 10 to a non - vertical section of flow or return heating pipe , as shown in fig1 . where the spacer is removed , caps 150 may be fitted over the plugs 142 . the connectors 136 may be separately fitted into each of the john guest ® speedfit ® connectors 98 and may be rotated through 360 ° to suit the angular path of the central heating pipe . for the separator device 10 to be most efficient it must be mounted in a vertical orientation with the bleed valve housing 106 uppermost and the drain valve 116 at the lowest point . the preferred and most common option is to fit to vertical orientation pipe but by removing spacer 144 the separator device 10 can be installed to a non - vertical cut section of central heating pipe by virtue of the flexibility of fitment 130 . in fig1 , fitment 130 is installed on the separator device 10 to receive a vertical pipe in the upper pipe socket and a horizontal pipe in the lower pipe socket . by virtue of the inlet and outlet connections being in - line , the separator device 10 is easy to fit . furthermore , the inlet and outlet can be interchanged , i . e . the flow direction can be changed , and the separator will operate effectively with flow in either direction . all of the separating chambers are able to cope with swirl in both directions within the housing . by providing three chambers filtration is achieved whilst the flow rate is substantially unaffected .