Plumbing Questions? Ask a Plumbing Expert.
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What is the model of the valve? does it have integral stops/shut offs?
I understand. I asked if there are integral shut offs. They would be where the water lines connect to the valve body.
Then there's no way to adjust/increase the flow. It's possible sediment could be fouling the cartridge but the valve should have been flushed out before the cartridge was installed. You can try removing the cartridge and flushing out the valve.
The integral shut offs are just straight screwdriver slots on the end of a short valve stem right where the water lines connect to the valve body.
Counter clockwise to open
Then flushing the valve is all you can do. Is the flow weak out of the spout too? or just the shower?
When you mix you're getting flow from both sides so twice the flow of hot or cold only.
If that's your concern then it may be normal operation
Do you have more questions?
I'd appreciate a favorable rating