Do I need Marble Impregnator

[Kendiy]

I am tiling 3 sides of 800mm shower tray. Around the middle of the tiling I will be placing a 75 mm strip of marble mosaic tiles (approx 0.3 sq m).
Tile shop says I need to use marble imopregnator on the marble tiles. But it is £15 for 1 litre when I only need a timble full.
Do I need to use marble impregnator in this situation where the tiles will only be exposed to water and soap when showering.
Is there something else that will do the trick but is cheaper?

 

[nellyb]

Yes you do need to use marble impregnator before grouting. A minimum of two coats in total.

It's not cheap stuff. Might be worth asking the shop if they'll seal them for you or sell you a thimble full if they have any open bottles laying around.