Also when I have done it myself in the past (hiring equipment) the carpets have appeared to get dirty more quickly 2nd time round. Is there anything you can do to prevent this?
That’s because the carpets are treated to help repel dirt, when you wash them you wash off this treatment.
And, according to the chap I had tround to clean a carpet, because the hire shampoo leaves a residue which dirt then sticks to.
I hired a chap with a 20hp(!) wet vac in the back of his transit, which he used to flush nearly boiling water through the carpet. No chemicals, the heat/water/pressure did it all, including removing the stain from a whole bottle of red wine spilt across the middle of the floor. Excellent job, and not much more than a DIY hire.