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Which supply line is hot/cold

I had a plumber rough in a new vanity and shower for me. He crossed the lines somewhere so now the hot is on the right for the sink which really is no big deal. I am concerned that the hot and cold for the shower valve is also backwards...how can I tell before I put up board and tile? I have tried to feel temperature differences even tapping on pipes but nothing has let me know...also this guy is licensed and was a family friend don't want him back in my house

Re: Which supply line is hot/cold

If he is a real plummer he will come back and reverse the lines for free. get him to check the shower while he is there also for free.

Re: Which supply line is hot/cold

Due to a family fall out i dont want him back in my house as i stated b4

Re: Which supply line is hot/cold

What make shower faucet do you have? If it's Delta or Moen you can fix the problem by flipping the cartridge.

Re: Which supply line is hot/cold

Can't you run the shower to see what is hot?
Reversing the lines to the sink shouldn't be that hard. Should be Easily DIY with a few tools and a little patience.

Re: Which supply line is hot/cold

Under the sink: no problem at all, you don't even have to switch the lines, just label them hot or cold with visible stickers or color ribbons.

Shower: as mentioned before, it could still work. If you have a 2 handle valve, you'll need to switch the lines, but first verify the positions of the hot and cold, just turn on the water long enough to get hot water.

A. Spruce
Re: Which supply line is hot/cold

Typical supply set up is exactly as a standard faucet, the right side is cold, the left side is hot. If this is not the case in your situation, then your installer is an idiot, licensed or not. While the problem can be corrected by reversing the cartridge or the supply lines to the faucet, this is NOT the way to correct the situation.

You need to have someone who knows what they're doing come in and set the supply lines correctly, then install your valves and taps from there.

Re: Which supply line is hot/cold

Sometimes, when you have back to back sinks, what's normal on one side (hot on the left and cold on the right), becomes the opposite on the other sink - and there you have it, a messed up under the sink plumbing.

I have had situations like these with houses I bought for investment, so I just tied red and blue ribbons on the hot and cold nipples. Problem solved. Cheap and easy solution.

However some shower faucets must be corrected, as mentioned before.

Re: Which supply line is hot/cold

Codes can require hot on left and cold on right- check locally. Sinks are an easy fix- use longer supply tubes and cross then over under the sink. Showers can be a bugger if you can't reverse the cartridge, especially back-to-back showers.

If your local codes require hot left etc and you've worked on that faucet, if someone gets burned later on you'll be getting burned too- by a judge and jury :eek: Anytime you work on something it and any disturbed surrounding areas have to be up to current codes when you're finished.


Re: Which supply line is hot/cold


The easy test - turn off the water going to the hot water heater (HWH) then turn on one or the other tap for a few moments allowing for the hot water residual pressure to drop. The cold will keep on running.

We carry red and blue electrical tape in our plumbing supply box.

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