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A new housemate likes to end her warm showers with a run of cold water. We've noticed there is a very loud whining/foghorn noise after she switches from hot to cold water, for the duration of running the cold water. I've read online about banging/pulsating noises when using hot water, but I don't think this situation is the same.

More detail: The housemate switches the shower settings from hot/warm to cold (the coldest setting) instantly, and our shower manages to change temperature with about a one second delay. The noise usually begins after that second's delay (i.e. as soon as the very cold water comes on), and lasts the duration of the cold water usage. It stops as soon as she turns the shower off completely. The noise does not seem to come from the shower head but from the pipes system itself. There is only a temperature knob for the shower, and no power setting.

Can anyone figure out what is going on and I'd be extremely grateful for quick fixes if there are any (aside from making her change her shower habit!). Thank you!

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  • Hello, and welcome to Home Improvement. Wild guess: many shower controls have a thermostat inside to keep you from getting scalded, and yours is malfunctioning. And, you should probably take our tour so you'll know the details of contributing here. – Daniel Griscom Sep 13 '20 at 9:59
  • Thank you for the welcome! The noise is not a warning noise but seems like a mechanical/plumbing related noise? – M Choy Sep 13 '20 at 14:14
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    Thermostatic valves (operating correctly) simply make the water not too hot. They don't make "warning noises." Thermostatic valves misbehaving make mechanical noises, and exactly where they happen varies with the misbehavior. It's not uncommon to have squeals and moans of various sorts when that happens. Often they can be avoided by small movements of the control (i.e. if your housemate went for cold but perhaps not "the absolute coldest possible setting" it might go away without changing parts. Otherwise, change parts, but I'm guessing this is a rental...so discuss with landlord. – Ecnerwal Sep 13 '20 at 15:58
  • Thank you for the suggestion. Will try asking housemate whether she is willing to not turn it down as cold as a quick fix for now. Will turning down the temperature more gradually also help? – M Choy Sep 13 '20 at 17:26
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With the flow on the cold being the issue it sounds like water hammer. I have seen extreme water hammer with very tiny flows but it is much more common with high flows.

The 2 solutions I know of for water hammer are. Strapping the pipes that are chattering, if you have access a couple of straps to keep the pipes from chattering will quiet it down. Add a water hammer arrester these are devices you install on the water line that have a chamber spring loaded or air chamber that cushion the flow issue. For best results they need to be on the line that is chattering but I have seen one installed at the toilet fix a shower & sink issue. These devices cost between 10-20$ in the US and since most plumbing is not accessible would be my first thing to try.

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If there are separate knobs for hot and cold water, it's possible that the washer in the cold water valve is loose. Disassemble the valve and tighten the screw that holds the washer.

If this is a single-handle mixing valve, you may need to replace the cartridge.

As a temporary fix, if the shower's water supply has its own shut-off valves, create the flow condition that causes the noise, then gradually turn the cold water shutoff valve until the noise stops while cold water continues to flow. Make sure the shower is still capable of mixing enough cold water to make a safe shower temperature.

If all else fails, install a flow restrictor between the shower arm and shower head, or a new low-flow shower head.

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  • Thank you! Would turning down the temperature more gradually help as a quick fix? (as someone in the comment above mentioned maybe not turning it down as cold as currently, so I'm not sure if this is a similar idea). – M Choy Sep 13 '20 at 17:25
  • @MChoy I don't think so, but it won't hurt to try. I think the noise starts when the cold water flow exceeds a certain rate. The shower head is a restriction that permits X units of flow per minute. When hot and cold are flowing together, the sum of the two flows equals the total flow that the shower head permits. Turning off the hot (quickly or not) allows the cold to flow at the full shower head rate. If something is loose in the cold valve, the higher flow rate starts the vibration. – MTA Sep 13 '20 at 18:53
  • I see - but then again as I mentioned the sound does not seem to come from the shower head or even the 'knob area' - but seemingly from the deeper pipes? Regardless I will try both suggestions! Because if we have just the cold water flowing initially, there is no noise - it only comes on after a period of hot water is turned off. – M Choy Sep 13 '20 at 19:16

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