Rough-In Plumbing Question about placement of hot/cold lines in ceiling/floor joist cavity

[isotope]

I just have a generic (non-code) question about running hot/cold supply lines in a ceiling/floor joist cavity. I have always wondered this about other professionals practice regarding the placement of hot/cold supply lines in a ceiling/floor joist cavity. I've never really thought about which line (hot or cold) should be higher when they are both running mostly parallel in the same ceiling/floor joist.

In a new construction situation... Assume that you have your main hot and cold supply lines running mostly parallel in a single ceiling/floor joist. So that you don't cross the hot/cold lines when inevitably some turns need to be made, you would have to run one line (ex: cold) a few inches above the other line (ex: hot) even though these lines are running mostly parallel in the same cavity.

As far as I am aware, there is no code requirement that mandates that one line (ex: cold) has to be placed higher than the other parallel line (ex: hot). So, I was just wondering. Do you guys have a preference which line you like to run higher in a long run within a ceiling/floor joist cavity?

 

[Terry]

Nothing in the codes tells you where to locate the hot and cold in relation to each other. I have always run hot high, cold low.
In a bathroom, the toilet is the lowest fixture, so right off you have cold being added first. It just made sense to stub out and run low for that.
In joists or on walls we would run hot high, mainly so that we didn't mix things up. Less thinking is always better. Now we run a lot in colored PEX, so mixing lines is a lot harder to do.

 

[Sponsor]

 

[isotope]

Nothing in the codes tells you where to locate the hot and cold in relation to each other. I have always run hot high, cold low.
In a bathroom, the toilet is the lowest fixture, so right off you have cold being added first. It just made sense to stub out and run low for that.
In joists or on walls we would run hot high, mainly so that we didn't mix things up. Less thinking is always better. Now we run a lot in colored PEX, so mixing lines is a lot harder to do.

Solid advice. I’ve worked onsite with other plumbers on large commercial projects and most of them say they just go by the builders CAD drawing or plumbing map plan, which is usually hot line above cold line. I was just curious how this tradition started.

But anyway, I’ve never really paid attention to which line (hot or cold) should be on top. Now, I’m questioning my most recent projects. From now on, I guess I will try to route the hot line above cold. For those situations where it’s just easier to do the cold line over hot line, is there any harm? It seems like this is just tradition and it is not code mandated, so is what’s the big deal routing the cold line over the hot?