I have a piper 100 pipe lazer, it wanders at about 300 ft up to about an inch. It has been in the shop 3 times they say there is nothing wrong. Using a fan helps a little but still is a pain. Especially when laying sewer mains that are real flat.
What type pipe, what size, and is it glue or slip joint.
we have the same laser. this is not a problem unique to the 200. we've had that with our old 4700's, 5700's, our topcon, etc...you're dealing with an air issue. we have an old furnace fan mounted to a piece of plywood that we set on top of the manhole crown and jam a lot of air thru the main. you can get dead air, hot pipe that's sat in the sun, being laid in cooler soil, bedded with cool sand/rock...pipe lubes, pipe glues, cleaners that can all deflect your beam. i've been around sewer lasers since the early 70's, and my experience has been to shove air to em.
Day is right and there is usually something mentioned about this in your owners manual. We use one of our gas powered burn fans to get some air in there with a few pieces of plywood, etc. to help point the air. We own 2 Weldco Beales burn fans, one old with a briggs and stratton engine and one newer with a honda engine. http://www.weldco-beales.com/ Here is link to one Weldco is selling on Ebay. http://cgi.ebay.com/*NEW*-FIRE-FAN-(Pocket-Cyclone)_W0QQitemZ250587312503QQcmdZViewItemQQimsxZ20100228?IMSfp=TL100228133013r24484 Also Weldco Beales is in Tacoma, Washington.
When we are digging especially in rock, we cover the end of the pipe with a rag to keep the dust out. Also laying a box fan on top of the manhole and blowing through the pipe works good to. Temperature change, glue fumes, moisture, and dust will deflect the beam every time.
Interesting, we have tried forcing air down it it does not fix it. Then we get out the old spectra in the exact same pipe and conditions and the beam does not move at all.