Question: Copper Pipe Threads vs Brass (Same?)

[Tidybuoy]

I'm wondering if the threads on copper pipe fittings are the same as brass.

I'm asking because I'm plumbing for my new Tankless Water Heater and the unit came with a brass fittings kit (i.e., parts that have valves and connect to household plumbing). I purchased 3/4" male threaded fittings that will be soldered to the copper input/output piping but they don't screw into the brass fittings very easily and start resisting after about 1-1.5 turns. Seeming like it's not a match, I tried threading in a 3/4" brass fitting and it went in fairly easily and started resisting after 5+ turns.

Anyone have experience with this? I'm wondering if I should be using a brass fitting with a sweat to copper connection? I can't find the installation manual for this and having trouble locating on net.

[craigster59]

Not sure, with copper vs brass do you need a di-electric union?

[cabmandone]

Yep.. NPT.

If you're worried, take one of your fittings to a box store and give it a try. It's possible the fitting you bought has bad threads. Wouldn't be the first time I've had that happen.

[hcoles]

Just be sure you don't mix parallel threads (hose bib) with NPT. NPT requires tape and/or goop to not leak. There are some hose assemblies with fittings that have parallel threads but they are meant to attach to NPT. Those have seals to make it work. I think I have that correct. ?

[hcoles]

I didn't answer your question. The NPT slip fittings NPT threads will match up with brass items with NPT threads.

[Tidybuoy]

Originally Posted by craigster59

Not sure, with copper vs brass do you need a di-electric union?

Dielectric is not needed between Brass & Copper but is required between the galvanized and copper - which I have done under the house to the main water connection. I'm not sure why but Brass does not conduct like copper to galvanized. According to my research, about 50% of plumbers use brass to connect copper to galvanized and the other 50% use a dielectric coupler - it's mixed opinions. My neighbor, who is a plumber told me that either works and so I'm using the dielectric fitting because the one I found is simpler and has the sweat fitting on the copper side.

Originally Posted by hcoles

I didn't answer your question. The NPT slip fittings NPT threads will match up with brass items with NPT threads.

Thanks all. I will double check tonight as it's possible that my threads are for hose fittings and not plumbing NPT.

I've been looking at internet photos and I see both brass & copper being used for the final connection to the water heater. Regardless, I am going to bring my connection fitting with me and make sure I get the correct final pipe connection before installing.

[look 171]

What a re you trying to do?

[dad911]

I used the kit for my tankless, makes it easy to flush.

https://smile.amazon.com/Rheem-RTG20220AB-Webstone-Tankless-Service/dp/B00C5YBENQ/ref=sr_1_3?dchild=1&keywords=Webstone+3%2F4+in+Brass+Tankless+Water+He ater+Service+Valve&qid=1621467875&sr=8-3

Are you going to copper or pex?

If copper I'd use the water heater supply flexible lines with sharkbite ends.

[Tidybuoy]

Originally Posted by look 171

What a re you trying to do?

I'm installing a tankless water heater to replace my old 1968 water heater. I'm installing it in a different room (next to the existing room) and so I have to make minor changes to my plumbing. I'm connecting the new tankless water heater using 3/4" copper pipe which will connect up to my galvanized plumbing under the house. Eventually, I may replace more lines with copper.

So now I have run copper up the wall and out to where it will eventually connect to the tankless but the ends of the copper have to be threaded and will thread into the brass coupler connection kit that ultimately hooks to the tankless.

Everything was going smoothly until I test threaded my fittings into the brass kit and they don't screw in very well and I was afraid I would strip the copper. The copper fitting will screw in 1/2 turn and then stiff where as a galvanized pipe will screw in 5 full turns before getting stiff.

This is a photo of a similar install valve where my copper line will connect at the bottom and the top connects to the tankless via a coupler.

[look 171]

you need this lil' guy https://www.lowes.com/pd/NIBCO-3-4-in-Copper-Threaded-Adapter-Fittings/3505128

[look 171]

Large pic of the connector at my home. Just shot that pic for ya, Vern.

[Tidybuoy]

Originally Posted by look 171

Large pic of the connector at my home. Just shot that pic for ya, Vern.

Curious how that re-circulation pump works. How much extra plumbing is required to install? Does this cause the tankless to run all the time to keep the pipes warmed up? Will insulating the pipes help with this much?

[look 171]

That was installed over 10 years ago. There's a thermo switch that's attached to the hot returning water line. Once it drops below a certain temp, especially in the winter months, it will kick on the pump. Since it doesn't get that cold here, it will runs for about 20 seconds, about 15 times per hour. I had a timer hooked up to it, but removed it because I realized it was running so little during the night. I pulled it to keep having too much crap there.

A return pipe is needed from various locations or the furthest point from the heater. Check valves are needed to keep water from entering back into pipes where you need to keep hot water out. Check valves do go bad over time due to hard water.

[john70t]

Originally Posted by Tidybuoy

. I'm not sure why but Brass does not conduct like copper to galvanized.

Brass is about 67% copper and 33% zinc(galvanizing).
It has the ingredients of both metals but it doesn't self-corrode which is kind of interesting.

Some pipe foam insulation sleeves and a WH blanket will help keep in the heat.

[Bill Douglas]

Originally Posted by john70t

Brass is about 67% copper and 33% zinc(galvanizing).

It can also contain about 2% lead