I am first time home owner facing a plumbing issue so any advice will help a lot.

Underneath my kitchen sink basin looks the photo below. Recently I was trying to adjust water pressure and all of sudden

  1. Hot water doesn't flow out of the connected kitchen faucet even when I fully opened the water valve
  2. Cold water over flow (pressure is too high) out of kitchen faucet even when I fully closed the water valve
  3. Oddly, hot water does flow into dishwasher and I can run warm (not as hot as it was before but hot enough) wash cycles.

I cannot pinpoint what is the issue here. I suppose the shut off valves are broken and needs replacement but how can hot water flow into the dishwasher? Does anyone have advice here?

under kitchen basin

  • How were you trying to adjust water pressure? Were you opening and closing the shutoff valves under the sink?
    – HoneyDo
    Commented May 16, 2022 at 2:48
  • 3
    Sometimes with older multi-turn valves the washers become brittle and break apart clogging the supply line.
    – HoneyDo
    Commented May 16, 2022 at 2:50
  • @HoneyDo thank you and yes I was opening and closing the shutoff valves. Clogging the supply line (connected to the facet) can explain why one line of hot water flows but another one doesn't.
    – camel_case
    Commented May 16, 2022 at 3:40
  • 1
    I would replace both of those valves with quarter turn valves instantly, Takes like 30 minutes each. Because you're going to have to undo the hot side anyway to see if something got stuck inside. Just need a couple of adjustable wrenches Commented May 16, 2022 at 3:52
  • @OutdatedComputerTech if the shutoff valve is soldered on or even if threaded, it might not be so easy to replace it.
    – Armand
    Commented May 16, 2022 at 15:45

1 Answer 1


I can't be sure from the photo, but it looks like your hot and cold pipes coming out of the wall might be plastic PEX or copper with soldered fittings. The shut off valves on each look like older multi-turn valves as @HoneyDo suggests. Those valves can be rebuilt in place, which I think may be easier than replacing them for a novice at least. In my experience, it's the hot water side where the internal washer breaks down and pieces can flow downstream and clog a faucet intake (BTDT!).

Assuming the above is the case, you have two issues to deal with:

1. The hot water shutoff valve probably will not fully shut off now, likely missing part or all of its internal rubber washer.

To fix this, shut off water upstream of that valve (perhaps at your hot water heater). Disconnect the hot water supply to the faucet at the connection circled in blue in the photo below (have a bowl and rags ready as some water will be dripping out).

Next, rebuild (replace) the internal washer on that valve or replace the valve. Rebuilding is surprisingly easy. Ask This Old House made a video that shows the process How to Rebuild a Shut Off Valve | Ask This Old House and rebuild kits or just the washer are easily available at hardware and big box stores. Just make sure to remove any remnants of the old washer before installing the new one.

Once you have your valve rebuilt or replaced, make sure it is turned off and turn the water back on where you earlier turned it off upstream. Make sure the valve is not leaking; fix if it is. Once the valve is not leaking, hold a rag and bowl over the disconnected end (blue circle area), slowly turn this shutoff valve on a bit to make sure water comes through and flush anything out, then shut it off again.

2. Now you need to backflush the faucet's hot water side to try to remove any clog.

The idea here is that anything that got pushed into the faucet intake is most easily removed by reversing the water flow and flushing it back out. In this case, we have the intake disconnected at the blue circle. Holding that loose end over a bucket to catch the water, set the faucet to medium water temp (halfway between hot and cold) and turn it on. Some water from the cold water side should flow through to the hot water side and down out the hot water intake, hopefully dislodging any blockage. You may need to put your finger over the faucet outflow to block it and force the water back down the hot water intake tube.

Hopefully you will see or hear a clog blown out and into your bucket. Once you've backflushed, re-connect the hot water supply line at the blue circle area, turn the hot water shutoff back on, and test your faucet.

enter image description here

  • 2
    In general I'd agree. However, I'm not sure where you're seeing PEX or any plastic plumbing in there. It looks to me like there's copper pipe (with some wall paint on it) coming out of the wall, soldered into the 90° valve, then compression fittings from there. Still a +1
    – FreeMan
    Commented May 16, 2022 at 11:50
  • @FreeMan Yes, I'm not sure if dirty PEX or copper or what from that photo. Not knowing exactly what it is, I'm not sure the OP would have a straightforward time replacing the valve, which is why I suggested a rebuild in place.
    – Armand
    Commented May 16, 2022 at 15:43

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