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Hot/cold water mixing in bathroom

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  • Jan 21st, 2022 12:56 pm
[OP]
Jr. Member
May 1, 2011
176 posts
30 upvotes
NORTH YORK

Hot/cold water mixing in bathroom

Hi everyone I've got a hot/cold water mixing issue in my bathroom. When I turn on the cold water faucet at the sink, the water comes out room temperature first (~1 sec) and then somehow heats up to lukewarm (2-3 secs) and then becomes cold as it should be.

There are two faucets (see the photos below), one connected to the shower and the other near the sink. Based on my own research, the shower is likely the one that's causing the issues due to the design and I'd need to replace the cartridge which I struggle to learn how (i.e. sizing, tools needed, how not to cause a flood..)...

My questions:
1. How do I go about figuring out the root cause?
2. How to fix it?
3. Any contractors might be able to do it? recommendations would be really appreciated.

Thanks a lot!!
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10 replies
Deal Addict
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Jan 2, 2012
4052 posts
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KINGSTON,ON
Your cold water line is routed past a heating duct, and is getting warmed.
It has zero to do with your shower faucet.

If you live in a single family home, you really should run your faucet until it is cold anyways. A home buit before 1975 with copper lines will have lead soldered joints. When the water sits in the lines, lead can leech out.
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Jun 18, 2020
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I wish my delay was that short. House 7ish yrs old and i bet it's 15-20 sec for some taps to get hot. Shower better, maybe 5 to 10. Even ones close to the tank, and midday with use, can take a few seconds.

I figured this was normal. Hope I'm not wrong...
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Jan 5, 2003
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Toronto
Most faucet problems are due to a faulty cartridge, so you're likely on the right track, especially if this is a recent problem and it was fine before. If it is the cartridge, it'll keep getting worse over time.

How do you control the temperature in your shower faucet? I only see three handles for the tub, handheld and shower, and a four spoke wheel for the volume. Is the temp control separate?
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Jan 2, 2012
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KINGSTON,ON
GTA12345 wrote: I wish my delay was that short. House 7ish yrs old and i bet it's 15-20 sec for some taps to get hot. Shower better, maybe 5 to 10. Even ones close to the tank, and midday with use, can take a few seconds.

I figured this was normal. Hope I'm not wrong...
jm1 wrote: Most faucet problems are due to a faulty cartridge, so you're likely on the right track, especially if this is a recent problem and it was fine before. If it is the cartridge, it'll keep getting worse over time.

How do you control the temperature in your shower faucet? I only see three handles for the tub, handheld and shower, and a four spoke wheel for the volume. Is the temp control separate?
You need to reread for context. OP is concerned about the cold water at the vanity faucet having a slug of warm water in it before it becomes cold.
It's super common for water supply lines to cross or share joist bays, or share bulkheads, with forced air ducting.
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Sep 27, 2006
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Not so easy there Ma…
hukejia wrote: Hi everyone I've got a hot/cold water mixing issue in my bathroom. When I turn on the cold water faucet at the sink, the water comes out room temperature first (~1 sec) and then somehow heats up to lukewarm (2-3 secs) and then becomes cold as it should be.

There are two faucets (see the photos below), one connected to the shower and the other near the sink. Based on my own research, the shower is likely the one that's causing the issues due to the design and I'd need to replace the cartridge which I struggle to learn how (i.e. sizing, tools needed, how not to cause a flood..)...

My questions:
1. How do I go about figuring out the root cause?
2. How to fix it?
3. Any contractors might be able to do it? recommendations would be really appreciated.

Thanks a lot!!

WeChat Image_20220118191033.jpg

WeChat Image_20220118191041.jpg
Had that in my kitchen at the previous home. Copper cold water pipe was run over the hot aìr duct for a long stretch. Plenty of warm water from the cold water tap in the winter!
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Sep 27, 2006
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Not so easy there Ma…
GTA12345 wrote: I wish my delay was that short. House 7ish yrs old and i bet it's 15-20 sec for some taps to get hot. Shower better, maybe 5 to 10. Even ones close to the tank, and midday with use, can take a few seconds.

I figured this was normal. Hope I'm not wrong...
Totally normal. Low flow faucets have been around for years and save water but add to the delay.

A slight help will be to add foam water pipe insulation to the first 6 feet of the run from your hot water tank.
https://www.consumerreports.org/cro/new ... /index.htm
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Jun 18, 2020
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MrFrugal1 wrote: You need to reread for context. OP is concerned about the cold water at the vanity faucet having a slug of warm water in it before it becomes cold.
It's super common for water supply lines to cross or share joist bays, or share bulkheads, with forced air ducting.
Hmmm. Right, opposite of my bathroom issue.

Of course, as my luck has it, I've got the warm water issue in my kitchen, often have to wait for warm to clear to cold when filling the Brita.

Sigh.
[OP]
Jr. Member
May 1, 2011
176 posts
30 upvotes
NORTH YORK
MrFrugal1 wrote: Your cold water line is routed past a heating duct, and is getting warmed.
It has zero to do with your shower faucet.

If you live in a single family home, you really should run your faucet until it is cold anyways. A home buit before 1975 with copper lines will have lead soldered joints. When the water sits in the lines, lead can leech out.
Thanks a lot. There is indeed an electric baseboard heater in the bathroom. Would the best way to check be to turn off the heater and see if the issue goes away or persists?
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Jan 2, 2012
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hukejia wrote: Thanks a lot. There is indeed an electric baseboard heater in the bathroom. Would the best way to check be to turn off the heater and see if the issue goes away or persists?
You can try if you want. There's no hazard to what is going on. You could just wait until warmer weather to see if this persists. My guess is that it will stop when the heating season is over.

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