Whenever I've had to do any work on our bathroom loo I've had an issue with the isolation valve (LH elbow) fitting. I just fitted a new float valve & it's OK but I get a drip drip from below the fitting where it mates with the valve stem coming out the bottom of the cistern. I replaced the previous fibre washers with a nylon one & while that has improved things I've still got this drip drip. The connection is straight on to the plastic fitting. No ptfe tape, no hemp etc. Should I consider that? The isolating valve part of the fitting is very fine as to whether it's on or off too & I wonder whether this fitting might need replacement - hard water area & the valve's been on there for about 15 years. Advice please to a not very good DIYer.