Waterproofing Xperia Z3 when reassembling?

"All the guides I have read state that the Z3 Compact will not be waterproof after opening it. You can check this buy entering this code to access the service menu on the phone:

*#*#7378423#*#*

Then you go to Service Tests -> Pressure Sensor

Make sure the flaps for charge port and sim port are pressed in. Press down on the screen or just squeeze the phone and the pressure should change if the phone is waterproof. It does not change much but if it does not change then the phone is not waterproof.

I have changed the back cover on two phones. What I found out was that you must have an original back cover adhesive. Use it even if the back cover comes with adhesive. Check on Ebay for ""xperia z3 compact adhesive"". If you are changing the LCD you must buy the front adhesive. The second time I used the original adhesive and the pressure test was successful.

Sony Xperia adhesive

I am not sure how much the pressure should rise on a new Xperia Z3 on the pressure test but I will go to a shop and test this on a new device. Then I can give a better idea of how much the pressure should rise on a new waterproof device :-)

I have an idea about using the heat gun on the back cover after assembling to maybe making the the adhesive more fluid and filling out all spaces. Not sure about this but the pressure test must be the final test anyway!

For the LCD I could not find any source for the LCD/digitizer only. It seems Sony original part consists of LCD/digitizer+frame assembly and not the LCD/digitizer separetly

##UPDATE on LCD and adhesive##

It is easy now to get hold of LCD/digitizer only. And I have good luck with replacing only the screen. Much cheaper. There are too many really cheap but crappy frame/LCD complete parts. I only recommend the original complete ones but they are really expensive.

I have experimented with different adhesives for screen and back glass. I find too much bad black adhesive, not being sticky enough and the screen or back coming off again. So I have tested the clear adhesive that requires heating. I use a heat mat or heat gun. This seems to be a good permanent solution. Like this search. Look for the clear one that says ""requires heating"".

##UPDATE on adhesive##

Like I commented I stopped using the black adhesive and always use the clear adhesive now. Use a heat plate since a heat gun can very easily damage the LCD."