Check your local codes. I can't imagine a local code demanding Stainless pipe for potable water, and galvanized is not frequently used from what I have observed. PVC, CPVC, and copper seem to be the piping materials of choice for potable water services.
The galvanized steel pipe and the coppper tubing would be commonly used for smaller sizes in residential installations. Some building codes might allow PVC and CPVC (for hot water) in residential installations.
Larger galvanized pipe beyond NPS-2 threaded might not be as available. Grooved coupling systems (Victaulic, Anvil) could be used for larger galvanized piping.
The PVC pipe might not be used for some commercial buildings and industrial plants. Heat tracing could be applied on the PVC if the temperature is limited by thermostats or integral limiter conductor cables. Steam tracing would not be suitable unless special techniques are used on steam tracers to separate tracer for installation.
Large size pipe for potable water could be carbon steel, coated / cement lined steel pipe, cement lined ductile iron pipe for buried service, plain ductile iron pipe, concrete pipe, PVC, or HDPE for long buried installations.
Stainless steel pipe might be used for potable water in food service / medical facility installations where washdowns are required.
ApC2Kp has most of the information that you need in his post. I would add that galvanized and copper piping would be the piping materials that are most effected by corrosion from poor quality water.
Thanks for your help on this matter.The more complete picture is that I am building a biodiesel plant which requires potable water for process purposes and drinking also.My tie in point is a 3" line almost one kilometer from the plant so my new 3" line will run above ground in a pipe trench to the plant open to the elements.Hence the electrical tracing and insulation if the line froze in the winter it could affect production of course.A last word on which material to use in this case would be welcome.
amanites,
The length and diameter along with the pipe trench installation would best be handled in HDPE. The possible external corrosion for pipe in a trench is no problem for HDPE. The HDPE could also be run under road crossings if required. The HDPE material could also withstand freeze without rupture in event of electric power failure to the heat tracing. A continuous flow through the pipe will keep it from freezing solid, unless temperature goes sub-zero. A heat trace system would protect line from plugging during a shutdown - it would be good to have drain provision in event of power failure in winter freeze.
That statement does not make any sense. Is this trench existing?
Why not bury the line? Most people avoid trenches because of the problems with them. If it is a new trench, the cost of the trench will be prohibitive.
What about fire protection? You probably need a large pipe for that.
Thanks for the input.The pipe trench is existing and has several existing pipes in it,it is an open trench about 1 metre below ground level.I looked into the possibilities of burying the line but its just not feasible as it runs through an existing site for at least 800 meters.You make an interesting comment about fire protection could you explain exactly what is meant,is it the risk of fire from the electrical tracing maybe?
Don't really think that the HDPE is a good application for the pipe trench. HDPE is suited for direct burial or you can lay it on top of the ground with stakes to retain the HDPE.
But in a trench with other pipes, and being insulated? HDPE is probably not a good application for that application. Plastic piping exposed to the weather is going to expand and contract with the temperature changes and the piping will move around, destroying other things in the trench as well as the insulation.
In a pipe trench with other piping, you probably are going to have to use a restrained pipe system.
In regards to the fire protection question, most facilities install larger pipes to handle the fire flow water requirements. The fire flow is normally much larger than the potable water or process water demands. What is the source of your fire fighting water?
Thanks again.The firewater pipeline is an underground system with hydrants all over the site.My tie-in point for the potable water line in question is in fact running from a neigbouring site and is not near the firewater line.I have read several pipespecs from previous projects and they have used galvanized pipe with screwed unions etc,but when I talk to my potential piping contractors during bid porposal meetings they seem to think that stainless steel is the way.
You have not presented enough information for someone to decide.
If the water quality as shown from water analysis testing or from previous experience is corrosive and aggressive, or perhaps there is a process issue where the corrosion products are not acceptable, then one would prefer stainless steel or galvanized.
If your pipe trench is in a damp area or floods, or is constantly exposed to water, then galvanized pipe will rust over time, then one would prefer stainless steel.
If the water is not corrosive, and the pipe exterior will be dry, then one would prefer galvanized.
The HDPE pipe that I was referring to in an earlier post was coiled HDPE. Coiled HDPE would not work because it is not restrained.
PVC and HDPE pipe systems will require pipe supports every 3-5 feet, so you would require lots of pipe supports to hold up the piping in your trench. So PVC and HDPE piping systems are probably not good piping options.
You might want to look into the use of FRP pipe, the pipe supports required are about the same distance apart as for steel piping.
Why don't you just have your contractors give you the price for stainless, galvanized, and FRP. Then you can decide.
