which metal for raw water use?

[mattnj]

which metal is the "best" to use for raw water flowing through it, of perhaps, which are the ones to avoid of the 3 below:-

I am playing around with something in my shed and not sure if ali/copper/steel/cast iron is the best/worst to use, i cant weld/braze stainless so thats out...

 

[mitiempo]

Bronze or monel.

 

[vyv_cox]

By 'raw water ' do you mean seawater? Copper is the only one you can even think about. My calorifier coil was 20 years old when I replaced it, copper coil, perfectly OK. But, and it's a big but, if you braze or silver solder it you are creating a nice galvanic cell and it will fail in a year.

 

[mattnj]

By 'raw water ' do you mean seawater? Copper is the only one you can even think about. My calorifier coil was 20 years old when I replaced it, copper coil, perfectly OK. But, and it's a big but, if you braze or silver solder it you are creating a nice galvanic cell and it will fail in a year.

is there another sort of raw water? Yes, i mean salt, so how are the calorifiers joined if they are not brazed or silver soldered?

 

[alan_d]

is there another sort of raw water?

Yes, fresh water. As found in lakes, rivers, canals etc.

 

[Pasarell]

I think you will find most heat exchangers are copper nickel, not pure copper, 70:30 is best but 90:10 is OK.

 

[cowpat]

is there another sort of raw water? Yes, i mean salt, so how are the calorifiers joined if they are not brazed or silver soldered?

Answer Bronze, For joining silver soldering is the easiest like 'easyflow' and is suitable because of it's silver/copper mix. electrolisis is not a problem, I expect the metalurgists will have to comment on this but if you use results instead of theory you can be reasured.
I build up propellers with it and the first one I did was in 1966. Chris.

 

[mattnj]

So if copper is ok, but not if its soldered, maybe i will try copper with plastic speedfit ends then?

 

[vyv_cox]

So if copper is ok, but not if its soldered, maybe i will try copper with plastic speedfit ends then?

A calorifier coil is just a length of copper pipe bent into a spiral. There is no brazing or soldering involved, except on the fresh water side into the tank.

Calorifiers from around 25 years ago were mostly pure copper. No alloying of any sort. My boat had one in it, corrosion free except on the fresh water side. The immersion heater blank corroded into its threads and could not be removed. When I replaced it I cut it open for interest. Check the photo at the very bottom of this page. Copper.

Since then a lot of stainless steel ones have appeared, often made by Italian companies. I can't speak for all of them but mine has a copper coil in it. I don't know how it is attached to the tank.

 

[vyv_cox]

Answer Bronze, For joining silver soldering is the easiest like 'easyflow' and is suitable because of it's silver/copper mix. electrolisis is not a problem, I expect the metalurgists will have to comment on this but if you use results instead of theory you can be reasured.
I build up propellers with it and the first one I did was in 1966. Chris.

I don't disagree that silver soldering a manganese bronze propeller doesn't create much of a galvanic cell and I would certainly not argue against your experience. That isn't the same as brazing copper tube, which the OP was talking about (I think).