I'm living at a 9th floor of a condominium and the water pressure at my 2 toilet at home were functioning very well all this while for 10years.

But recently, 1 of my toilet is experiencing a very low water pressure at the shower only. Whereby the sink and the pipe are running good in the same toilet.

I tried to changed the shower head but the water is still dipping slow.

I wonder, will it be the water heater in the toilet has spoiled or the problem with the pipe.

Please advice.

Your shower diverter may need to be rewashed or could have a blockage within the diverter itself, your going to have to take it apart.

Since, if you had a shower/tub, the diverter blocks the tub spout, I doubt it is the problem. More likely it is in the controls. Both single handle and separate hot and cold come apart about the same. Pry the little plastic cap off the knob, remove the screw, and knob. That reveals a nut. Shut the water off and remove it. A brief shot of water will flush out the crud blocking your flow. Having a helper hold a towel over it will reduce the mess to be cleaned up. Take a good look at the cartridge you removed. If it seems to be clogged too or has worn rubber parts, you may want to try to find a new one at the hardware store.