31 Jul 2000 at 11:41 pm #273281MasterPlumbersKeymaster
We are an industrial water treatment consulting company.
What are the advantages / disadavantages of installing galvanized pipe vs. schedule 40 mild steel pipe in a domestic
water line with regards to the following issues?
1 – Price
2 – Resistance to general corrosion
3 – Resistance to corrosion via over-chlorination
4 – Resistance to galvanic corrosion
Any assistance at all with these questions would be greatly appreciated.
– Dan Morgan
Technical Services Manager
1 Aug 2000 at 1:06 am #287265
Sir with all due respect you are slightly confused as to material.
You see mild steel is never used on domestic water as the oxygen would cause major rusting problems.
The schedule like 10, 20, 40, 80, 120, is the internal wall thickness. Thin wall like 20 is used in some fire suppression systems and schedule 40 is the normal piping whether it be galvanized or black steel.
Galvanized pipe for all intensive purposes is nothing more than black steel with a zinc coating (hot applied) Unless your talking Yalloy, Or Galvanized wrought Iron GREAT STUFF
On high water pressure systems we use Galvanized schedule 80 and on high pressure steam we use schedule 80 “black”
1- Price Galvanized cost more
2- Resistance to general corrosion— Galvanized is more resistant UNLESS connected to brass or copper then you get an electrolytic action and on Yellow brass you get dezincfication
3- Resistance to corrosion via over-chlorination —- The Zinc may react as it is more active then iron and may turn to zinc chloride .
Generally WE never use black steel on FRESH water no matter what the schedule.
I hope this helps.
4-Resistance to galvanic corrosion —black steel cant have “galvanic corrosion” BUT it can rust in the presence of oxygen
1 Aug 2000 at 1:10 pm #287266
Are you aware of any regualtory restrictions regarding the coupling of galvanized and copper pipe in a domestic water system?
– Dan Morgan
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