Can’t seal shower valve

[Richieduliban87]

When trying to mount a shower valve onto these two 3/4” tap extender fittings, the washer ends up getting destroyed and washer leaks out immediately. What am I doing wrong? I have tried both rubber and fiber washers.

 

[Alec_t]

Can you show us the mating part of the shower valve?

 

[Richieduliban87]

 

[terryplumb]

Show the washers ,fitted into the valve as pic above ,and show not fitted also.
And show a clear picture ,in close up ,of the end of the fittings mating surface please.
Is the joint into wall end watertight ?

 

[Gasguru]

Ditto, close ups of the mating surfaces needed. What's happening with the exposed threads at the tile face?

 

[Madrab]

Possibly overtightening .... try hand tightening the nuts until fully hand tight then 1/4 turn with an adjustable.