Grohe Single-Lever Faucet delivering very low pressure when set to "Hot"

[rsilverst]

Hi there,

I have a Grohe single-handle faucet that was professionally installed about 3 years ago. I am not 100% sure of the model, but it looks very much like the Concetto on their website, and I have attached a couple of photos of it (as well as a video, linked here). We've been having a problem with this faucet for about a year now. The water pressure when set to fully "hot" is about 50% that of when it's set to "cold". We've verified this by checking volume of water dispensed in 30 seconds, and the cold volume is about double the hot volume.

We have no issues with hot or cold water pressure elsewhere in our house. In fact, our bathroom faucets are fed off the same plumbing line as the kitchen, and have strong pressure on both hot and cold water.

I have checked under the sink to make sure all the valves were fully open, and that nothing was leaking or obviously misconfigured. Also, as I noted, this worked perfectly for the first couple of years but then deteriorated.

I am interested to know if it's possible that the valve inside the single-lever itself may be malfunctioning so that the hot water is not receiving maximum flow. As a related note, when I set the valve to "hot" the faucet makes a small humming noise, and that noise dissipates if the valve is moved from hot toward cold. See video here.

Thank you for any guidance you can provide!

Bob

 

[billshack]

There could be a variety of reasons.
remove the aerator and check for debris, turn on faucet with out the aerator and let her rip
next
1) go under the kitchen sink and turn off the hot and cold water valves.
2) disconnect the two speedway going into the faucet.
3) get a big bucket and put the speedways inside and then open them full bast .
if you have a good flow then remove the handle and disassembly the guts
if the flow is not so good the problem is upstream.

 

[Jeff Handy]

Very likely the faucet valve cartridge is partially clogged.

The hot side of any faucet is almost always the side that plugs up faster with minerals.

Grohe will send you a new valve cartridge.

You can consult with them to identify which exact faucet valve you need.

Youtube will have good videos showing how to change the cartridge.

Grohe website may also have videos.

Sometimes the under sink shutoff is partially clogged.
Closing and opening it several times might clean it out, while the faucet is fully open.
This also might release mineral chunks that clog up the aerator or flow restrictor or check valve, all located in the faucet somewhere.

They can be cleaned out or replaced if clogged.