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Must galvanized hydrant pipes be painted before burying?





January 10, 2012

Q. Dear,

Is it required to apply primer or paint to the galvanized underground piping for a hydrant system? We can direct server-wrap the pipe.

Amar Basha
- Saudi Arabia



simultaneous January 11, 2012

A. There's no straight yes or no answer to this. It depends on the soil conditions.
If slightly acidic, then you'd need to do something. Paint is one solution, but so are wrapping, plastic, powdercoating bitumen and some other coatings.

We have powdercoated galvanized water pipes for underground use in the past.

geoff_crowley
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
crithwood logo



January 12, 2012

A. Sir:

Yes it is required to prime with zinc rich paint and then overcoat with good quality paint at the connection between galvanized pipe and the brass valve. It is also required to have a 1 cubic foot to 2 cubic foot hole under the hydrant to collect water from the weep hole (frost protection). I wonder why you are using hydrants in your country where frost is likely not an issue.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA


April 6, 2012

A. Sir:

I am currently replacing four hydrants constructed from galvanized stand pipes. These galvanized pipes have 2 mils of zinc on them (I helped the pipe galvanizer attain these thin zinc coatings, BIG MISTAKE FOR ME). These hydrants failed after 2 to 5 years and all are corroded through where the galvanized pipe screws into the bottom brass valve. In the dirt holes all the stainless fittings and red brass fittings are perfect with no corrosion whatsoever.

I purchased four new hydrants all with red brass pipes (outer and inner pipe) at a cost of $450 each. With the back hoe (mine) and my hired guy, the total cost to replace each hydrant is about $1,000. Thus I strongly recommend all red brass pipes in hydrants. A bottom drain chamber filled with large rocks is required for the weep-hole water to drain downward. I like a 4 inch schedule 40 PVC vertical pipe around the vertical hydrant pipe to protect the hydrant. I fill the space between the two pipes with clean pea gravel.

Hot dip galvanizing has many, many useful purposes, but a hydrant is NOT one of these.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA



April 6, 2012

Wonder if we answered the same question or not.
Perhaps it would help if you defined what you mean as a "hydrant" ?

geoff_crowley
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
crithwood logo



April 10, 2012

Geoff,

For me a "hydrant" is a stand-pipe (usually hot dip galvanized) that sticks out of the ground (vertically), has a brass valve 5 feet down in the ground. The usual total length of the "hydrant" is seven feet. When the hydrant is shut off the vertical section of the pipe is drained by a weep hole also 5 feet underground. Thus this "hydrant" can be used in very cold climates. The "hydrant" is a common fixture anywhere in the USA having cold winters.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA




Can't paint internal area of welded GI water pipe

June 17, 2015

Q. Dear sir
I am working for a project in which we are using a GI Pipe for the supply of water from water tank to firefighting equipment. The dia. of pipe is 114 mm and the head is 60 m. For the joining of pipe we are using welding with electrode of 7015. My apprehension is that due to small dia. we can't paint the internal surface of the weld joint, due to which the joint may get rusted. So please help me in this regards.

Best regards,

Ali Hassan Shigri
Consultants - Skardu Pakistan


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