Need Plumbing Help - Common Sense No Longer Applies To My Sink Valves

This is insane. I have a fairly new waterfall faucet with split handles in our bathroom. I'm going to explain it in terms you folks will understand.

It worked fine for the first year, but then the flow rate just started to fall off at WOT. Oddly, the flow rate was better at 1/4 throttle but finicky as hell to balance in that spot. I thought it was the ceramic valve going bad or clogged, so I unscrewed it to find...nothing wrong. Ceramic valve flows like straight pipes when you blow through it. It doesn't turn past the throttle stops, so it isn't choked itself back down. Put it in the faucet, turn the valve open and it flows great for a second...then falls off to a trickle.

So 1/4 throttle = great water flow, WOT = crappy water flow.

For a test I choked the flow to the faucet using the wall cutoffs and I'll be damned if the flow didn't INCREASE when you close down the cutoffs a little. So crank both the faucet ceramic valve and the cutoff to WOT, lower flow. Choke it off at the cutoff valve and the flow IMPROVES with the faucet at WOT.

WTF...

The only thing I can think of is somehow the higher flow is doing weird hydro physics magic inside the ceramic valve housing and blocking the out flow. Trying to figure out if I can re-jet the ceramic valve like a carb using different discs inside.

Many faucet manufacturers have lifetime warranties on their products.  My first move would be to call the manufacturer, or contact them via email.

1988RedT2 said:

Many faucet manufacturers have lifetime warranties on their products.  My first move would be to call the manufacturer, or contact them via email.

I went full GRM on my shopping and got a bargain, warranty was only for a year (and I bought it in 2018).

This is the unit: https://www.homedepot.com/p/BWE-8-in-Waterfall-Widespread-2-Handle-Bathroom-Faucet-With-Pop-up-Drain-Assembly-in-Spot-Resist-Matte-Black-A-96556-S-Black/314274463

I got it on sale for something like $45 at the time.

Screen clogged and higher water pressure gets through maybe? I'd try it with the screen off and see if it behaves the same way. Assuming of course there is one :)

I found this!

I pulled up the 1-star reviews on the H-D link you sent me.  You are not alone!

Hope the video helps.  Good luck!

Another one about a clogged aerator in the cartridge.

Thanks 1988RedT2, I'll give those a try. I may also see if I can swap in a washerless cartridge instead of the ceramic unit. I just need to find one that is the same diameter and seat depth.