Laser Level Accuracy Issues

Laser levels can be knocked out of whack, and old-school water levels can have issues of their own. The watchword is "trust, but verify." October 19, 2014

Question (WOODWEB Member) :
I was recently installing a giant kitchen and using my PLS laser. Something seemed wrong and my intuition was right, my PLS laser was out of level 3/8" over 30 feet. I checked the return policy for PLS and it made me angry. I met have heard tell of a very good German brand of laser for installing cabinets that is durable and accurate. I am willing to spend some dough on a really kick ass laser if I can be confident that I donít have to pull out the Stabilas to double check every layout line I set. I should say that I install high end kitchens and millwork where small fractions around a room really count. Any brand and model suggestions?

Forum Responses
(Cabinet and Millwork Installation Forum)
From Gary Katz, forum technical advisor::
I feel your pain. I've been there and lost my patience and my temper a few times when I've found a level or a laser wasn't accurate - yet it was pretty late in the game to realize that. I check my lasers frequently. When the laser is new, before you start taking it out to jobsites, shoot a benchmark in your shop or your home - pick a workbench or a countertop or a mantelpiece or something that never moves. Be sure you have room to cast the laser line a good distance in two directions, then mark the spots on the wall and spray them with lacquer or something. That's one of the biggest problems with lasers. They've become smaller and smaller, so we carry them in one hand and treat them like regular tools, but they're sensitive instruments.

There are three companies that I know of that make accurate lasers: PLS, Hilti, and Stabila. I use the Stabila lasers because they have an on/off switch that is also a pendulum lock, so when the instrument is in your truck or tool box, it's not rattling the pendulum all over the place. Like I said, they're sensitive instruments. They must be treated with care.

From Contributor O:
We have Bosch with a pendulum lock. We paid under $300 for it, and so far it's been accurate. It gives 360 degree level and plumb plane readings. That's a lot for that price. I also have a PLS5 that needs to be re-calibrated.

From contributor G:
We have a Bosch GLL2-80 and are very happy with it. As mentioned it has a pendulum lock that protects it during transport 360 degree vertical and horizontal lines and can be used with their receiver out to 260' and 65' without . It self-levels and has a longer warranty than the Stabila.

From contributor M:
I have been using the Hilti and have never had a problem and Iíve had very good customer service. To check for accuracy on your laser level set your laser on one side of a room (the bigger room the better) and about midway mark on the wall or use masking tape where the line is. Then take the laser to the other side of the room and point it the other way. Line up the line on one of your mark and check if the laser lines up with the other mark. If it lines up on both side then it's good. If not have it calibrated.

From contributor F:
The ancient Egyptians got it right a long time ago - water level. Had a really bad especially with a laser years ago on a very high profile job and have sworn them off since then. A drop of dish soap in each end of the hose eliminates the water tension curl for complete accuracy.

From contributor Y:
I had the same experience as Contributor F and went back to water level. You should have seen the looks on the carpenters faces on the job - they had never seen such a thing. We used to use them for metal framing on commercial jobs. Around the corner, out of sight and they still work. I canít get the guys to remember to bring it in out of the install truck though so itís frozen half the time. I did just order another laser though and am going to give them another try. Maybe they have improved and are a little more rugged now.

From Contributor A:
Iím pleased with my Stanley cross line level. Iíve had it for a few years and it seems accurate enough and has good battery life. The type mounted onto a telescopic pole spring loaded up to the ceiling. Having read this thread though I will make an effort to check it periodically.

From Contributor J:
I'd ditto Gary - been using lasers for years "trust but verify". There's no way in the world I'd start a big complex (and expensive) cabinet installation without first checking my equipment to make sure it was accurate. Despite having the laser, we still use a water level extensively with cabinet installations - and the first thing I do is lay out my perimeter line with the water level - then set up the laser, check it to the water level line and then go. The laser is much faster once it's confirmed 'all systems go'. We use PLS equipment.

From Contributor S:
You can get into trouble with a water level. Consider the following: A sunny kitchen. Lay out your level lines. Park the level. Now part of the loop is in the sun. Water warms up. Water in a black line can be 30-50F degrees warmer. Water expands about 300 ppm per degree C. So 25 C is 7500 ppm, or about 7 mm per meter of hot hose.

Meanwhile: A rubber hose contracts when it gets warmer. So if you took your gage back to the start, you'd see something really odd: Not only would one side be higher than the other, but both would be higher than the original mark. It can get worse. Suppose you didn't go back to your control mark, and the whole tube got warm. You started with eight meters of hose. Now the whole hose is 20 C warmer. The hose is shorter because the rubber contracted, the water column is longer because the water expands. One percent of eight meters is 8 cm.

This is why I prefer the system where you have a large container as one end of the water level, instead of just another tube. For one thing, if you suspect the water of warming, you can lift the hose and run it all back into the container, and refill. If you are going to be serious about using a water level, you need two tubes, and an itty bitty pump to circulate the water so that it is even in temperature.

This one bit me last fall when I was working outside. It was just freezing. The shady end of the level was starting to get slushy, while the sunny end wasn't exactly toasty, but it was nowhere near freezing. That expansion of water into ice takes place over about four degrees. Slushy water is lighter but warm water is also lighter. So after cutting one post a quarter inch short, I checked every five-ten minutes to see what the difference was when I went back to the original mark.