Not replying to anyone in particular, just replying on the last message.
The tank on my carpet cleaner only holds a couple of litres, which I did complain about and is what most complain about on the product review site. BUT, in hindsight, I think they did it that way so it was easy for anyone to use. Mine is a single tank that has a bladder in it. The clean water goes into the bladder and the dirty water goes in around it, so they don't mix. It lets you know when it's full and you just take it off and tip it out of the spout at the front. I empty it outside into the drain under the tap as I don't want to tip it down the sink or bath because it's disgusting. I then refill the bladder in the kitchen sink. If the waste tanks is getting dirt building up in the bottom, I'll take the top off and give it a quick spray out with the hose.
I did have issues the first couple of times with the carpets staying really wet and the next morning they were still damp. So now, once I've washed, I run over again with some plain water (no detergent) to get any excess soap out. Then I run over again slowly with no water to suck up any excess water. It's surprising how much comes up by doing this. I could easily lift 2-3 tanks from 2 rooms of excess water. Even in winter, the carpets dry very quickly. In the living area where the heater is on, dry within an hour. Rooms with no heating, 2-3 hrs tops (usually closer to 2).
I did clean once with just hot water as I'd run out of detergent and I was surprised how much carp that got up too. If there's stains on the carpet, you can get stain removers, but I find holding the cleaner over those bits for a minute or so and going over them a couple of times gets them out.
I walk backwards with my washer and drag it backwards as it seems to do a much better job than pushing it forwards like a vacuum. I watch the water being sucked up and if its hit a dirty spot, I'll go over that bit a couple of times until the water goes clear. I go over each section twice. I'll nudge it up against the wall, activate the water, drag backwards for a few feet, release the trigger to stop the water, then push back over that strip back to the wall. That helps suck some of the extra water up. I'll then repeat. After the second go, I'll push it back to the wall and not activate the water when I drag it back again, I'll just let it suck the excess out of that strip (I still go back over it all again once I've finished washing to get the extra excess out).
When I move onto the next strip, I overlap a little bit. I've probably made it sound a lot more awkward and cumbersome than what it really is, but I can get the 3 main rooms done in a couple of hours (loungeroom, dining room and I have awful carpet in my kitchen).
I really think the secret to quick drying is going back over it to suck excess water out. I've had no problems since I started doing that. They don't tell you that in the books, but it does work.
Another advantage to having your own washer is, if you have a fish tank and it explodes, you can just suck the water up (I haven't had fish for years, but did have one explode a lifetime ago and I ended up calling the fire brigade to come in and suck the water up. I did ask if they were busy first). If you tip water over on the floor for any reason, pet drinking water or whatever, you can just suck it up. You don't have to find a heap of towels to sop it up. It also works out a lot cheaper in the long run if you have inside animals and want to keep on top of it, especially when it's been raining and they bring their muddy little feet inside.
My step sons house sometimes floods when they get a lot of rain. I told him to get one as they would have towels laying around everywhere. Now they just suck the water up and saves a lot of time and effort.
