I've assembled quite a nice arrangement of standard round black drainpipe bits to take water off a flat roof via guttering and down pipes, into another gulley, round the corner, down another drop etc....into the patio drain which works beautifully, but suffers from drippage where the various joins and bends are pushed into each other. Is there a specific product I need to get to securely join and seal the bits, or can I used a standard gutter sealant? The ones I've seen all seem to call themselves emergency repair which leads me to believe they're just a temporary fix until some proper permanent repairs are done.