Solar heated water overflow

My PVC guttering has recently developed a leak at the point at which the overflow from the solar panel discharges into the guttering. In addition the external underside of the guttering between the point of the leak and the downpipe has become noticeably discoloured. On the face it would appear the two are connected.
Am interested to hear from anybody who has encountered this problem and how they dealth with it.
Thanks

Overflow? Is this a solar thermal system or PV panels?

It seems like your system is dumping excess heat by releasing hot water into your gutters. This water could be 80 degrees +.

It should be possible to alter your solar system to release water from your hot water cylinder. This could be done by installing a motorised valve on the hot water pipe under your kitchen sink or bathroom, and releasing the excess hot water down the waste pipe.

Another way would be to use your central heating coil in the hot water cylinder to dump excess heat into your radiators.
This can be done by setting the solar controller to switch on your central heating circulation pump when the hot water temperature reaches a set level.

Solar thermal system.