Drip leaky galvanized pipe

[DougP]

I have a 100 year old house that has slowly been upgraded over the years. Some galvanized pipes still remain.

Coming from a new hot water heater I have 1/2" copper pipe (new) that is spliced into a 3/4" (or maybe 1") galvanized pipe - which then has about a 20-30 ft straight run into a tight crawl space in my dungeon. At the end we have a bathroom with your typical sink, toilet, shower stemming off the main pipe and then the main pipe has an adapter which connects to 3/4" copper pipe. From this 3/4" copper someone put a Sharkbite connector to join the copper to PEX (3/4"). This is where the renovations begin and everything else is in PEX 3/4" until it needs to branch off. The branches are 1/2" PEX going to the faucets etc.

On to my question:
I want to get rid of the galvanized pipe because it has a slow drip leak spot and it's an old galvanized pipe. I want to replace it with a 3/4" PEX. My concern is going from the 1/2" copper from the water heater, into a 3/4" PEX. I have read that the i.d. of 1/2" copper is similar to i.d. of 3/4 PEX. If so, I don't think there is a problem.
Should I just cut the copper coming from the water heater, and us a sharkbite connector sized to connect 1/2" to 3/4" (copper to PEX) at one end, and 3/4" PEX to 3/4" copper at the other end? Will the size, going from 1/2" copper to 3/4" PEX to 3/4" copper to 3/4" PEX to the rest of the house be a problem? Thanks.

The other option I'm considering is cutting the 1/2" copper at the water heater and going right to 1/2" PEX to replace my galvanized pipe. But after this pipe, remember that the new construction PEX is 3/4"

 

[Jeff H Young]

I cant see your picture but basicaly running your entire house off 1/2 inch is not good proper sizing why you think smaller is better i dont know. Id say 3/4 minimum both feeding water heater and leaving the heater with hot . Get rid of the 1/2 inch copper go bigger

 

[Sponsor]

 

[Reach4]

1/2 inch can supply hot to a lavatory and a shower/tub. If more than that, upsize.

 

[Jeff H Young]

1/2 inch can supply hot to a lavatory and a shower/tub. If more than that, upsize.

Its more than that its the entire house

 

[DougP]

I cant see your picture but basicaly running your entire house off 1/2 inch is not good proper sizing why you think smaller is better i dont know. Id say 3/4 minimum both feeding water heater and leaving the heater with hot . Get rid of the 1/2 inch copper go bigger

I would prefer this as well but the water heater was recently professionally installed and although the input and output look like they were set up for 3/4, the installer stepped both down to 1/2 right off the water heater to join with the other existing 1/2 copper. It's attached in a way that looks very secure and something I don't have the experience to mess with.

So basically, that's my question in a nutshell. Is it a bad idea to go from the water heater's 1/2" copper into a 3/4" PEX trunk which then branches into 1/2" PEX for all the fixtures? Thanks.

 

[LLigetfa]

Chances are that the 100 year old galvanized pipe is internally constricted down to less than 1/2". Friction loss is size over distance, so the greater the distance of small diameter pipe, the greater the volume and pressure loss.

Ideally, you should use at least 3/4" from the meter, through the hot water tank, all the way to the 3/4" PEX trunk. If you are not comfortable doing it, hire a professional that won't take shortcuts and use 1/2".

 

[Reach4]

Given the 1/2 is there, no problem stepping up to 3/4 for cold. For hot, 3/4 holds more water, so once you branch off to the lavatory or shower, it would be best to then drop to 1/2 again. 3/8 pex to the lavatory hot would be even better, but that costs more and may need more tools and adapters. So that is not often done.

IMO, if you are not seeing negative symptoms, then don't worry about that stretch of 1/2 copper.