Have seen it done both ways
Why the question
We have dry system with schedule 10 pipe installed 20 + years ago, over the past few years multiple leaks have occurred in mains and branches, due to capital expense we are just trying to get input from others.
Not a sprinkler contractor, but
1. Have most of the system assessed internally to see how it looks.
2. Maybe replace only horizontal pipe, which is more than likely where your problem is.
3. From now on get a good sprinkler company to inspect it and make sure it is drained.
We started mandating Schedule 40 pipe on dry systems, to hopefully make them last longer.
Dry system problems occur mainly because of lack of maintenance. We have been fixing dry systems for more than 30 years and have found that trapped water due to lack of service causes corrosion of pipe. Get on a proper maintenance schedule of at least twice a year, which minimize major repairs.
For replacing the entire dry system, one, it is not cost effective and usually never needed, two, repair the pipe as needed and add additional low points drains with more frequent service. Unfortunately, not all initial installations correctly pitch the pipe back to the dry pipe valve, so additional low point drain valves should be added with re-pitching of pipe. 18.104.22.168.1. All low point drains, 22.214.171.124.3, should be located in a heated area, if not in a heated area, the other alternative which also requires maintenance is heat tape with insulation. You must have both. Either one with the other is another freeze up waiting to happen. 8.16.4.
As cda cda mentions find a good contractor, there are many out, but only a few can properly fix dry systems.
For type of pipe, sch 40 or 10, galv or black, we've seen all fail with the same main cause of failure, no maintenance.
any replacement should utilize cut grooved piping, additionally look at nitrogen systems to reduce the oxygen in the system
We do not install sprinkler systems, but do inspect and repair systems. We find leaks in schedule 5, 7, and 10 systems. To date, we have found no leakage problems with schedule 40. When replacing pipe, we use less than 21 foot sticks, often using pipes short as 6 feet. We install hangers at the end of the pieces for support and to keep the pipe level.
On a recent job with 4" pipe, we found "bath tub rings" indicating the pipe was not level or draining. We often install more drains.
My opinion, 5, 7 and 10 should not be allowed. but we know cheap is popular. I like to see the roof insulated, then dry systems are not needed. Also if heavy plastic sheeting is tented over the pipe, and stapled in place, with insulation over the plastic, dry systems may not be needed. I just lost a job replacing dry pipes, one leak at a time. They hired someone to replace all the schedule 10 in the attic. My reaction, great! I do not like to crawl attics.
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