Grohe question

The situation. Grohe shower valve. One handle for the hand wand, one for the shower head. When the hot water is turned on, even though the pipes are copper and the water heater is VERY close, the water trickles for a while and then seems to build pressure after 30 seconds or so and then everything is fine. All other bathrooms and faucets in the house are perfectly fine. So, the problem is the delay in pressure.

Tips?

THANKS IN ADVANCE

remove and clean the cartridges in the valves? clean inside of the shower heads?

Fixed

FIXED! Pulled the cartridge, the screens were clogged. I said the hell with the screens, cut them off, put it all back together and now it works perfectly. Lesson of the day...

If the crud gets into the cartridge, you'll end up replacing it...much more costly than cleaning the screens once in awhile. They are there for a reason. The bigger question is why do you have big enough chunks of things the screens can trap.