Hep2O Shutoff Valve leaking

[MrDuck]

My newly acquired home has a number of Hep2O shutoff valves installed for use as service valves for taps etc. But the first one I tried using immediately developed a leak. I quickly opened it again and I think the leak has stopped (!). Is this a common finding and is the valve repairable? I am tempted to open and close the valve several times but might this make things worse? I an a newbie to plastic plumbing so any advice welcomed.

This is not the first time I have found a service valve more unreliable than the appliance being serviced...

 

[flameport]

Very common that such things leak, the cheap metal ones do the same. They are not repairable, replacement is the only option.