The bottom annular end of a vertical collar that extends into the vertical tubular portion of a T-housing and is fastened therein by resilient fingers extending radially outward from the collar, is contacted by a resilient finger of a filter inserted through the collar into the tubular portion, a radially inward extending shoulder in the collar is contacted by the bottom of an annular horizontal plate on the filter, and a liquid level alarm system housing is attached to the outer surface of the vertical tubular portion by a plurality of vertically spaced apart catches or studs received in slots on the alarm system housing, a tapered pipe having a first end fastened to a horizontal exit joint on the T-housing and a second tapered end force fit into an exit pipe of a septic tank.