conditions under which the device is expected to operate the sealing o ring 49 is received in the ring 41 as shown in fig1 which also has a resilient flange 52 capable of a slight degree of radially outward deflection to provide a snap in assembly over the annular ridge 53 at the upper end of the neck forming the air inlet 35 this ridge also engages the ring 49 the lower o ring 54 may be slipped over the neck of the air inlet as shown in fig1 to supplement the seal between the ring 41 and the air inlet but the snap in relationship at the flange 52 and the effect of the o ring 49 may make the lower o ring 54 unnecessary the upper o ring 49 however should be of very soft material so that the relatively light forces involved in the positioning of the air valve 34 would be sufficient to make the seal at this point effective an o ring of sponge material or tubular in cross section will increase the capability of the o ring to accommodate itself to the slight changes in position of the valve referring to fig5 7 three different container configurations are illustrated which may be used to suit various tank installations in fig5 the large lobe 55 of the container has a lateral extension 56 with an accordion pleated portion permitting extension to the dotted line position to reach the end of the tank to provide the largest capacity for the container within the available space in fig6.