Bathroom sink Q

Hi All... We recently moved into a house built in 1970. A bathroom in the finished basement occassionally has an awful sewer gas/sewage smell - but not always. At times the smell is minor, at times it can give you a headache and all the windows need to be opened. Here's some relevant info: - the toilet is loose - when you stand up after sitting on it, it rocks back - when we had a plumber come once, they felt there was no venting for the bathroom - the sink is hooked into a utility sink drain pipe which then hooks into the drain pipe for the washing machine. He couldn't find a vent for the toilet - we're on a septic tank that was drained prior to us closing on the house - and the inspection showed no problems - the other bathrooms have no problems - when the toilet is flushed, it flushes very slowly and has a lot of bubbles coming up from the drain - the smell seems to lessen when we've covered the drain and overflow drain in the sink with tape Ok, that's all I can think of. any ideas? Thanks! Ben

I need to know how to let air in the holding tank for our water in the house. Our water keeps shutting off. My ex used to do this each month but is no longer available. It is important that I do this before the motor gets burned up. Your help will be most appreciated. Thank you.