First some background;

  • our house was built in '56 and has galvanized pipe
  • Hot water heater is almost two years old
  • We finished remodeling our kitchen last July and installed a new sink and faucet (Grohe 32665DC1 SuperSteel Concetto Single Handle)
  • The lines running to the kitchen are linked to the faucet and the dishwasher.

The water pressure for the kitchen sink was always fine. It's no firehouse but it doesn't need to be. However, in the last couple of months it has decrease to just above a trickle. I've opened up every possible inlet/outlet on the faucet to clear rust and it appears to be fine. I disconnected the flexible supply lines and ran water through those. There doesn't seem to be any obstruction but the pressure there is still lacking, although seemingly not as bad as at the faucet.

I don't know where else to look for an obstruction. The faucet itself was/is low-flow but this is ridiculous. The water pressure everywhere else in the house is fine so it has to be isolated to the lines running to the kitchen. I've experienced an episode where I was running the dishwasher and the sink at the same time and caused some 'jackhammering' in the lines. Shutting off the sink stopped the "hammering".

I intend on having the galvanized replaced with PEX at some point but it isn't in the budget right now. I'm hoping there is a way to clear the lines for the time being.

I am not experienced with plumbing. I've read quite a bit on the web but I don't like working with the galvanized for fear I'm going to make something worse.

I'm very close to calling a plumber but I want my ducks in a row if I come to that point so I'm not taken for a ride.

Any thoughts from the hive mind? Craig

  • 2
    I understand you checked all the lines, but there was no mention about the aerator screen. That will be the first thing to clog, other than the galvanized pipes.
    – Jack
    Oct 13, 2015 at 6:34
  • 1
    Check the aerator as Jack mentions first. If that's not gunked up, you might want to just replace the galvanized line supplying the kitchen. You haven't described your plumbing at all; so I'm guessing here, but typically it's set up in a trunk and branch type manner. So you'll have a larger (3/4"-1") trunk, then smaller (1/2") branches feeding fixtures. Replacing the kitchen branch, might be enough to get you going for the time being.
    – Tester101
    Oct 13, 2015 at 12:02
  • 2
    Take a look at what can happen to Galvanized pipe after 60 years... Corroded pipe almost blocked If most of your pipe is half that bad, a chunk of scale can break off and get lodged in an elbow causing a rather abrupt loss of flow.
    – JPhi1618
    Oct 13, 2015 at 13:33
  • Just to reiterate, you are very probably at the end of service life on 60+ years of galvanized pipe. Make a plan/budget now and be ready for a complete re-pipe. (There's nothing worse than having to scramble to arrange a major job like that.) Oct 13, 2015 at 14:10
  • 2
    The problem occurring shortly after experiencing line hammer is no coincidence, you most likely have a debris issue. Oct 14, 2015 at 5:09

1 Answer 1


Since the pressure drops for both hot and cold at this fixture, the problem is inside the fixture as you've already guessed. The first place to look is any aerator or filter screen on the fixture, debris gathering there will quickly slow the entire flow. Looking at the diagrams for your faucet, I believe that will be part P (the flow straightener) in this picture (Q appears to be a tool for opening the end of the spray assembly).

faucet assembly diagram

You can also verify the pressure from before the fixture is strong by disconnecting the hot and cold supply and running them into a bucket or drain to check the pressure coming from after the shutoff valves.

The problem could also be in the mixing valve and you'd need to remove and inspect the cartridge if it's there. basically anywhere after the two water lines merge could have a blockage.

  • As I commented above, I checked the faucet head at point O and P. I saw one small flake of rust that was removed. I also pulled the mixing valve (in-line cartridge where the lines meet) and I didn't find any debris. I also pulled the lines off the faucet and ran them into a bucket - the pressure isn't ground breaking but it seems the flow is stronger than I'm seeing through the faucet.
    – CraigPDX
    Oct 13, 2015 at 18:38
  • 1
    The "seems the flow is stronger" comment concerns me. Get a large bucket, put/note a mark partway up, and time how long it takes to fill to that mark directly from the shutoff valve lines (without the faucet), in the sink with the faucet, and from other fixtures in your home where you have good pressure.
    – BMitch
    Oct 13, 2015 at 20:05
  • The flow from the lines is definitely stronger. I've called Grohe and they are sending me a new cartridge. At the same time I'm going to get some quotes on re-plumbing the house with PEX.
    – CraigPDX
    Oct 21, 2015 at 20:35

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