the present invention is directed to unclogging drain lines in asphalt distributor trucks and trailers . referring to the drawing , the asphalt distributor truck or trailer 10 comprises a tank 12 containing flowable asphalt or similar material 14 which are to be dispensed on road surfaces and roof tops which flowable asphalt or similar materials then solidify or freeze on the surfaces creating a protective seal against precipitation , such as rain or snow , from penetrating into the underlying surfaces . the tank is made of steel , or an alloy containing steel , to withstand the high temperatures of the asphalt or similar materials being in a flowable state . the tank 12 is conventionally equipped with a drain line or hose 16 to deliver the flowable material away from the tank for distribution to said surfaces . accordingly , the drain line or hose may be short , such as a few inches , or it may be several feet up to 100 and 150 feet depending on the distance of the surface to be coated . at the end of the drain line or hose there is a valve 18 for opening and closing the flow of the flowable material emanating from the tank 12 . the exit port for the hot asphalt may have an extension hose 16 ′ attached thereto to transfer the hot asphalt from the asphalt - containing tank to a more remote site , such as a roof on the top of a building . in this case the pressure device is attached onto the remote end of the extension hose . the pressure device 20 preferably attached to the asphalt containing tank 12 , or to the extension hose 16 ′ when blockage / freezing occurs in the exit port . the pressure device 20 is carried on a handcart carrying a cylinder having 50 to 80 cubic feet of nitrogen or other inert gas . the pressure device is provided with a coupling chain which attaches to the exit port and safely holds the pressure device to the exit port . the pressure device 20 contains a nitrogen or other non - flammable gas in a tank 22 . the tank is equipped with a valve 24 and regulator gauge 26 to controllably release one of said gases when unblocking of the asphalt - containing drain line or hose 16 is required . the pressure device 20 further comprises a hose 28 extending from the regulator gauge 26 towards the truck valve . the end of the hose is equipped with a camlock coupling 28 releasably attached to the truck valve 18 . the pressure device is further equipped with a gauge 30 to measure the pressure originating from the tank 22 ; a relief valve 32 to relieve the pressure in the pressure device ; and a vent valve 34 which serves as a safety exit for overpressure . the details of source materials in connection with the present invention are as follows . relief valve 32 supplied by advanced specialty gas equipment by allied / kunkle valve industries ( s / n a0335549 - 1 - 1k ) having a pressure / temperature limit of 3 to 400 psig /− 60 ° f . to 300 ° f . ; valve and regulator gauge 24 and 26 manufactured by wika having 0 - 160 psig , operating temperature − 40 ° f . to 140 ° f . ; camplock coupling 28 manufactured by dixon , made of aluminum , maximum pressure 125 psig ; drain line or hose 16 manufactured by parker / dayco under the tradename dayco hose ; compressed nitrogen in cylinder 22 is widely available from suppliers , such as chapman gas , erie , pa . a having 40 ft . 3 capacity . the pressure device 20 is conveniently carried on a handcart equipped with chains to securely hold the nitrogen cylinder and associated items to attach the pressure device to the asphalt distributor tank or trailer . the method of use of the pressure device 20 to dislodge a plug of asphalt from the drain line or hose 16 of the asphalt truck or trailer 10 comprises the steps of : closing the valve 18 on the asphalt tank or trailer 10 ; attaching hose 16 ′ on pressure device 20 using the camlock coupling 28 onto drain line or hose 16 of the asphalt truck or trailer ; setting regulator gauge 26 on pressure device to zero pressure ; closing the vent valve 34 on hose 16 ′ of the pressure device ; increasing nitrogen pressure up to 90 psi or until blockage is dislodged ; removing pressure device 20 from truck valve or trailer 18 . the above description is intended in an illustrative rather than a restrictive sense . variations may be apparent to persons skilled in the art without departing from the spirit and scope of the invention as defined by the claims set for the below . parts list distributor truck or trailer 10 tank of truck or trailer 12 asphalt or similar material 14 drain line or hose on asphalt truck or trailer 16 hose on pressure device 20 16 ′ valve for opening and closing the flow of asphalt 18 pressure device 20 tank of pressure device 22 valve on nitrogen tank 24 regulator gauge on pressure device 26 camlock coupling 28 gauge to measure pressure in system 30 release valve in system 32 vent valve in pressure device to release pressure in system 34