Sometimes the rubber of the valve becomes sticky with time and dirt. I've had success using a silicon spray and Pledge Spray furniture polish on the inside so the valve lips no longer stick together. EITHER WILL DO.
Reviving an old thread…
How much water should be needed in the inlet area to the front roof drains for flow to start?
I found my passenger side front roof drain needed to be filled almost to the level of the base of the canvas before flow would start through it (clearly wrong). When it had enough head of water, flow would start and it would flow really well (you can tip a 2L bottle through fairly quickly), and empty with a gurgle.
But then after a few minutes it would again need a big head of water to get flow started.
Flushing with hot water and washing up liquid didn’t help.
I then syringed in and out through the drain inlet which improved it.
It now starts to drain when the inlet area is just full, both passenger and drivers side (see photos).
My question is: what level of water should be needed in the inlet area to the roof drains for flow to start? Should it start flowing into the drains as soon as it covers the drain entry holes? Or is it normal to have to fill the entry areas full (to get enough head for the outlet valve to open)?
The level I now need for flow to start is just below the level of the black plastic covers over the drains, so you don’t realise the entry area is filling up before flow starts unless you remove the covers.
I’m not sure if I’ve fixed the problem, or if flow should start into the drains with much less water in the entry area.
It’d be good to know what others find as normal before I try removing the scuttle cover to silicone spray the outlet flow valves.
Thanks!