Water pressure very low

Lime has build up

There is a nut up under the counter its hard to see but tighten that . Most faucets come with a special tool fo hat but can be done with wrench

Clean the faucet aerator.
Always run your tubs first so junk in lines comes out tub spout, then faucet taps last with aerators removed.
http://waterheatertimer.org/Low-hot-water-pressure.html

Gene
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If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

I have the same problem and have the fix. There is a water pressure regulator on the bottom of the faucet( under the sink) this part is bad. Grohe will replace it for free. Call Grohe at630=582=7722 tell them the model # of the faucet and the color of the regulator, they will send you a new one for FREE.

It sounds to me like sand or buildup in the cartridge. You should pull the faucet apart and clean the cartridge.

If it is just this faucet and no others then it is likely the filter screen in the tap head is clogged.

Remove the cover from under the tap head. Pries off from the tap head directly where the water comes out.

There is a metal mesh screen there. It will be full of white chalky deposits from minerals in the water supply. Clear that out and you will be good to go.

You will also want to clear the holes for the spray pattern. The same deposits will be there.

Good luck.

If this helped give you some direction please rate the answer for me.

Thanks.

HOT WATER IS ALWAYS A LOWER PSI THEN COLD WATER THAT IS OK

1. If by replacing the flexible hose you mean the hose for the pull-out portion - you have more than likely kinked or bent the supply line to the hot (left) side of the faucet.
a) If this supply is braided, then simply shutting of the water supply, removing the braided line and either replacing or attempting to straighten it out will be your best bet.
b) If the supply is copper, you will have to cut the line cleanly and carefully. you will then most likely need a 1/4" or 3/8" compression/quickconnect BY 1/2" IP fitting to complete your repair.
2. Other possibilities include:
a) Failure inside the faucet body which will most likely be warrantied by Grohe if you push them hard enough.
b) A problem at your hot water tank, most likely the outlet side and *perhaps* you hadn't noticed the problem elsewhere.
c) The hot valve failing to reopen fully despite all appearances; applies if you turned off the water under the sink for your repair.

when you installed did any teflon tape or debris get inside? you can remove and reverse flush with hose and it may clear the blockage

remove aerator and cart. and soak in limeaway over night