How big is the rug? Smaller than 1 metre... vac as thoroughly as possible, then put in bath with half a cup of washing powder, and some warm water,, scrub it with a brush,, rinse rinse and rinse again, this will rake about 30 mins, let the water drain off then hang it outside somewhere on a dry , windy day, it will look amazing.
If larger than 1 metre it will be to large for the bath , and too heavy when wet, so , vac as much as poss, sprinkle washing powder on it , use an ordinary garden hose to wet it , scrub with a clean broom , rinse rinse again with the hose, this is best done on a sloping area, to let the water run off, then hang to dry on a warm windy day.
I have used this metod on smoke damaged , and water damaged rugs for several years, on items where shringage/damage is not an issue , I have found the results to be very good, and have never had shrinkage/ warping/distortion of rugs. It may cost ooooo 50p in cleaning products.