Hi MoominmammasHandbag
Tony the carpet cleaner here.
I hope no one minds me posting here! My wife uses this forum, she showed me this post and thought I should put my professional point across :)
The black lines around the edges of your carpet could be two things. a) it could be a build up of dirt that has accumulated over the years (its akward to vaccum out! or b) it could and more likely be filtration marks.
Filtration marks are easly removed by any half decent carpet cleaner, BUT the mark will probably reappear i'm afraid. Maybe a month or several months down the line. The only way to stop them from reppearing would be to lay ply board down over the floor boards, creating an air tight environment thus stopping dirty air flow. These filtration marks will very likely appear even if you buy a new carpet!
The "my carpets get dirty quicker" myth. Two things, when you buy a carpet it might of had a protector applied to it. This protector on average lasts 2-3 years. Since your carpet is over 7 years this has probably worn away. A 7 year old carpet thats not been cleaned before will be a worn carpet. A good carpet cleaner will be able to bring the carpet up to a very good standard i.e. removing stains, pollutant, soils, grime etc fully sanatising the carpet. But the carpet will still be a 7 year old carpet. The fibres of the carpet will be worn so
As long as the carpets are thoroughly flushed out leaving no residue in the carpet then they wont get dirtier quicker.
Machine like bissel, vax and the dreaded rug doctor are very poor at cleaning carpets. They are highly underpowered in both extraction phase and putting down product stage. I have a long list of ex-rug doctor/bissel users as customers now :)
My advice to you is to get a professional carpet cleaner in. Its back breaking work doing trying to do a good job with a hire machine. A pro will charge between £30 - £60 a room depending on size of the room, condtion of the carpet, type of carpet etc. A hire machine is around £40 once you've bought the detergents.
Let me know which part of the country your in and i'll put a message on the a carpet cleaners forum that I take part in.
Thanks
Tony