CJ wrote:

I have a flat rubber roof that leaks very badly when it snows and then
rains. It happened twice this year during two storms between Feb and
March. The weight of the snow and rain somehow must pull the rubber
away from where it should cover the roof from the outside elements.
When it rains hard it never leaks.

There is a vent pipe and a square opening with cover (to gain access)
near the leak.

Any ideas on what to do?

CP

I'd guess it's the square access hole where the problem is located.

The membrane had to be cut and patched to create a curb, and since
melting snow is higher than rain alone, it's leaking at a particular
level.

Take a look he

http://www.watertighttech.com/produc...print_full.htm

This manual shows how it should have been done, so you'll be able to see
what's required to fix it.

Patches, adhesive and such are all available locally, and DIY is easy.

Remember, if a roofer can do it, it sure ain't rocket science.