Does water heater need to be first from supply?

[OnlyinCali]

Oddly enough, I’ve searched for roughly half an hour and found nothing on this topic.

Question-
Does the water heater need to be first in line from the street water supply line? I thought it was ok to branch off of the incoming (from street) 3/4” supply for cold water before meeting the tank, but my house has a good 30ft of “extra” copper. The hot water heater is the first to receive water from the street. They then doubled back with the hot and cold pipes, to areas which could have already been supplied with cold water from the supply line from the street. Is this necessary?

I can’t see a purpose to this extra copper “backtracking” right next to the the incoming supply but I figured I’d ask the pros before screwing things up with my repipe.

If it matters, incoming supply is 3/4” copper as well as the rest of the main runs, with 1/2” copper the fairly short branches out to sinks/shower/etc.

 

[Jadnashua]

You want a full diameter cold supply to the WH, but it doesn't really matter where it comes from, and you could run the cold from wherever you wish. But, consider that 3/4" copper is good for about 12gpm on cold and 8gpm on hot, if you follow the Copper Institute supply guidelines. Depending on what is in the house and how it is laid out, a 3/4" supply line might be undersized.

If you keep the length of the hot/cold supply lines similar, there won't be major differences in pressure caused by its length between the hot and cold. Depends on the volume used and the total 'effective' length of the pipe, which includes not only the pipe, but the flow rate and fittings (fittings create increased effective length, and thus pressure drop during flow, but not at static conditions).

So, depending on the maximum volume, you may or may not notice any differences, but it has a chance of being more even if you return after feeding the WH so the supply line lengths are closer to the same. If your inlet supply line is big enough, you'd never notice any difference.

 

[Sponsor]

 

[Dj2]

3/4" main line is enough for 1 bathroom house (with kitchen, washer and 2 hose bibbs). With 2 bathrooms, it's a good idea to have 1" main line water supply.

The water heater doesn't have to be the "first in line".

Normally, plumbers use the least amount of piping necessary and the shortest way necessary. If you have a ton of pipes, combine pipes and eliminate the unused ones. Keep the ones you eliminate, copper is valuable.

We can't tell what is useful and what is useless without seeing what you have.

 

[hj]

The water heater goes WHEREVER the builder designed a spot for it, even if it is the LAST item in the system. Saying the heater has to first makes a much sense as those who say the toilet had to be last. IF that were the case, it would severely limit how houses could be designed.