There are US Standards that need to be met when installing a toilet and Taylor Plumbing and Heating licensed and experienced plumber will know this and install your toilet to these standards  
 
A toilet installation mistake could end up risking your drinking water. A plumber will know exactly what to do and how to avoid any contamination to your drinking water.  
 
Installing a toilet on your own means simple mistakes can be made and one simple mistake could leave you with a sewage leak – which is not only unsightly but also unhygienic. Don’t risk it.

Setting the cistern water level correctly is also very important and not doing this correctly could leave you with an overflowing pan and more trouble.

It turned out the late guest was a Taylor Plumbing and Heating plumber and he went on to explain the risks of doing a toilet installation without a plumber.