I recently drained my older (1980's) Kohler tub and replaced the blower motor.The old blower worked fine just a few weeks ago but I had to replace the motor. The new motor is 1HP like the original. The new blower only activates the jets in 1 of the 4 seats. It acts as if the blower does not have enough power to overcome the water filled air passages.

Also, the 2" line from the blower loops thru the handrail then goes down an enters the tub from the bottom. The water level in the line is the same as the tub indicating there is no check valve (I physically do not see one, but I'm not certain what to look for) or if there is a check valve it is not working.

I also had the GFCI trip when moving around in the tub land grabbing the handrail last night, this was a first.

Any thoughts? Thanks in advance!

Standard blower installation is one check valve and one hartford loop, or 2 hartford loops (plumbing loop above the water line). Occasionally you can get water building up that went over the loop and accumulates in the plumbing, you can release the water in the bottom of the loop by drilling a small bleed hole.

Based on your observations it may be water in the lines, the blower should be able to move the relatively small amount of water at the end of the lines in the tub.

GFCI tripping is strange, take a volt meter and start looking for stray voltage.

Adding to what JEFFZ stated about drilling a small hole for a "weep hole" to let the water out, you can help prevent having any type of back draw by drilling a small hole at the top of the hartford loop as well. If you have a check valve, it will usually be located between the blower and the first hartford loop. You will see this as a large "bulge" in the pvc, about 3 1/2 inches for a 2" blower line. It isn't part of the pipe, it's something added in. It will also have an arrow on it indicating the direction of the flow. Not all spas have this, as a lot of older spas only relied on the hartford loop.

Thanks for the help, it appears I just have the hartford loop with no check valve. This blower problem is getting weird. I removed an inspected the 2" blower line, up to the point where the water level is at. Everything looked fine, no obstruction or leaks. I drained the majority of the water while keeping the blower running. As the water level lowered the additional jets began to work as intended. I drained the water until all jets were working fine to purge any possible airlocks. As I added the water the jets began to shut down, as if the blower isn't providing enough pressure to overcome the water. Only one jet had been working until this morning while sitting in the tub it just shut down as well. The blower sounds fine. I'm not sure what is going on?