I found the name of such a tool:
Nipple Stub Extractor Wrench,
which can easily removes broken
risers from PVC tees.

I will try to buy one tomorrow.

Peter

: As long as the riser was not glued in, any hardware store has a riser remover wrench to extract it.

: : I have a underground sprinkler system in my lawn.
: : A PVC riser was broken, which was connected
: : a spray head to a PVC tee underground.
: : The PVC riser is 1/2" in diameter.

: :
: : Now I have difficulty to remove (unscrew) the two
: : broken pieces of the PVC riser from the spray head
: : and the PVC tee, respectively.

: : Could you you tell me where to purchase
: : such a tool or how to remove the broken
: : pieces?

: :
: : Thank you.

: : Peter Xu