No they dont screw right up ,its only a plastic casing so dimensions can vary of the nut and thread ,i think the problem you have is the diaphragm in the throat ,these things are tempremental at the best to say the least ,i have had a coulpe of different types with a weight flapper for the best description and the other with the rubber mouth and they are all the same they dont do the job right as they stop ,the best one i have found is a german one ,well what else do you expect and it likes a tank with tracks and it works from a 12v supply .but the machine has its own built in filter and these are renewable ---at a cost-- So iam back to the old fashioned way as the best because i find that in the heat here in spain leaving the motor running for long periods causes the bearings to run hot and seize after a while ,so i use the motor and filter to skim pool for 1/4 of an hour every hour or so on the timer (summer setting) and once ever 4 hrs winter setting then once a week i **** the bottom with the manual brush yes i still have the pool cleaner but i only use it in the winter when its cold and raining and even then only for a few hours at a time to conserve electric and my pump .The best pool cleaner i have is the neighbours ,they have no pool at the back of me so he sends his wife over to help out as iam always out working and my mrs will not come out the housein the sun ,I use very little chlorine maybe a 5 kg bucket a year as i fill the pool with copper sulphate and i have a 10 mtre bore hole that i fill the pool with and this water has a 2% salt content so i use a salt converter to chlorine which works when the timer comes on to skim the pool ,unless its windy it very rarely gets dirty now .