Insatller setup my Kohler Toilet (#11451) and after he finished the installation the back of the water closet was 3.5 inches away from the back wall. He said the waste line was set 12 " from the wall as stated in the specifications. If so shouldn't the back of the watercloset be flush with the wall?

You are going to have to do some investigations...

It could be any of these..
#1 Pan to waste pipe connection
#2 Water flush to pan connection
#3 Cistern to water flush connection
#4 Cold water connection
#5 Cistern overflowing
#6 Condensation

If the cold water valve/washer is faulty then the constant flow of cold water is going to create a lot of condensation.

If the leak only appears after you have flushed the toilet then it is likely to be #1, #2 or #3

Just a matter of elimination..

there is either air in the line or trash blocking the water flow

If I understand correctly, your water level inside the bowl is 3 or 4 inches from the top of toilet seat?
Sounds peculiar to have that water level since you would get splashing etc.
That is not sanitary, and would be a code violation.
Look at side profile of tank.
Look at porcelain behind bowl and you can see outline of "s trap."
This is the internal trap that each toilet has built in.
Purpose of trap is to a) set water level inside bowl and b) just like a sink trap, seal pipe from sewer air from entering home.
Photo shows trap on sample toilet, with line showing approximate level of water inside bowl.
Since photo is at an angle, the line appears to go downward instead of level. Again the line is approximation, and photo intended to show where you can look on your toilet.
Your tank should have similar s-trap feature. From the feature on your tank, you can see what level water is intended to be inside bowl.
Some more expensive tanks, outline of s-trap is not apparent.

If the water level is so high that you experience unsanitary conditions, this is a code violation, and toilet should be replaced.

Quick web search turned up Kohler contact page: http://www.us.kohler.com/general/contact.jsp
KOHLER Customer Care at
Phone: 1-800-4KOHLER (1-800-456-4537)
Hours: 8:00 AM - 5:00 PM (Central Time) Monday to Friday
You can refer Kohler to this link on Fixya so they can clearly understand issue.

order a water pump. so the preasure of the water can suppy the requirements pressure of your water closet

As long as this toilet is NOT a pressure assist toilet. Then it probably has a water saver flapper that you can replace with a non water saver flapper. This will allow it to flush more. Be advised you may have to adjust the water level after the change to prevent it from double flushing. Hope this helps.

Hacked off the old seat? You mean the closet flange that connects to the sewer pipe?
That's the part that has the bolts. They go up through the toilet base.

If you have just a straight sewer pipe now, you can connect a new closet flange to it.

1.Hardware stores sell a rubber sleeve. This sleeve fits over the cast iron, or copper, or plastic PVC pipe, and the new closet flange has a stem that fits down in the sleeve. There are two large hose clamps, that come with this rubber sleeve.

The rubber sleeve is an adapter. It adapts the 4 inch sewer pipe, down to the 3 inch stem on the closet flange. (Toilets are known as a 'Water Closet', hence the flange that the toilet bolts to, is a 'Closet Flange')

Whatever size of rubber sleeve you need to adapt two pipes together, they have it.
The new closet flange is made of PVC plastic.
(Poly Vinyl Chloride)
The flange itself is about 1/2 inch thick, and has provisions for bolts. (Use Toilet Bolts, and nuts)
Be sure the closet flange sits flush to the floor. The 1/2 inch thick rim of the flange, sits on top of the floor. The flange is then screwed to the floor with countersink head screws. The slots allow the bolts to just slip in.

IF, the flange Does Not sit level on the floor, and the area for the toilet base is not level, you need to make a flat, level surface!
Do Not half step this, or you'll have a toilet leak from now until the time you fix the floor!

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Hrm, I see what you mean and this may be a bit late.

The 14" rough in is not standard (as in 12") and the depth (from the back of the tank to the front edge of the bowl is your concern here?).

Kohler also has a Sterling brand with the Windham model. This will sit on the 14" rough and measure less than 30" from the back wall.

You could also go with a Toto ($$$ concerns) as they have a unifit system that allows for adjustment from your roughed in closet/toilet flange. It basically mounts to your flange and then sets back 2" or 4" depending on which model Toto toiler you are installing. The Soiree-?sp may be your best bet for depth concerns, but not so good for your wallet.

Chris

low water in the bowl is only caused by the float being to high! the gurgles is Usually because of air coming back up through the pipe, check your vent pipe that come out the roof. this will help the draining.

Kohler is correct. The most likely cause of this problem is an obstruction in the common vent stack that both toilets share. When you flush the old toilet it need more air to flush and will get it from the easiest source (your new water saver toilet). First adjust the float level in the old toilet so it won't use as much water or just stick a brick in the tank to take up space.Second, run a snake down the vent stack from the roof to check for obstructions. Birds will sometimes nest in there.

This, or after you broke the seal of the wax ring, the water that was in the trap has voided. It's normal to have a good amount of water rush out when you first remove the toilet. That and there is still a bit of water in the tank and once you remove the fill valve, it escapes from the hole that is left. Proceed to install the new toilet and everything should be okay, just clean up the old water.