Grout for between paving stones

Hi
We put down a new patio last autumn with indian sandstone paving slabs (600 X 600 sawn edge). The supplier recommended using a sandy type grout that you brush into the joints and wet with a hose. The problem is that now when I try to powerwash the patio all this sandy grout keeps getting washed out of the joints. As the stone is black it needs to be powerwashed regularly.
Does anyone know of a normal type grout that can be used outdoors with this type of stone and will withstand powerwashing? Is there any issue of needing expansion joints etc (patio 30m2)?

Thanks,
Liamm

pop on over to www.pavingexpert.com for advice

When I 1st put down the patio, we did it the old way as described on the above, ie coloured cement, but recently like you there's stuff to brush in that sets though we didnt wet it. I've powerwashed it no problem but I dont over do it.

I know there are different brands, but the one I've used can be got in landscape depot tallaght

S.

I "grouted" my paving last weekend, using the advise from the site above I used Rompox brand of brush in stuff. very easy to use and has taken a hose wash ok. I'm leaving it a week or two more before power washing it.

I bought it from garden centre off the Asbourne road exit on M50. Guy up there stated the follow the instructions to the letter, especially to make sure then the depth of gaps to be a minimum of 25mm. maybe OPs grout is thin, ie just a few mm....