What is not cheap is getting a system installed with all the approved piping etc. I plan on doing all the pipe runs myself before the drywallers come in.
I just wanted 8 heads, one for each bedroom and then to cover the escape routes as well. I know the system won't be professionally designed and I don't intend to pass it off as a sprinklered home, but after watching a duplex across the street burn down I wanted some protection.
I ended up with 18 heads, basically protecting most of the house. Don't have final costs for materials yet, but will post if anyone is interested.
Lots of things to consider, like, I wanted to just run the sprinkler pipe to a toilet so it would have water flowing through it regularly and won't have to flush it. But then I can't use a flow switch ($100). The flow switch will be hooked to my alarm system and call me if it is activated. I don't want a phone call every time my son flushes his toilet.
You also need backflow prevention($150), you don't want stale water getting back into your drinking supply.
The piping used is PVC rated for high temperatures, it is dyed orange. Typically it is 1 inch diameter, some systems are 3/4", but that may not be enough water.
You might not have enough water anyway since alot of residual water meters are 5/8 inch.
Think it thru, my original intent was that if one head popped and put out a fire it was all worth it. But there is alot of planning and design.