how do i wash kotatsu futon?

I was wondering how to wash my kotatsu futon. If I was in america, I would just put it in the washing machine and dryer and be done with it since it's like a quilt. It kinda smells bad... so I need some way to get the smell out.
How would you do it?

You can bring it to a coin laundry, or a dry cleaners if you like.

the biggest washing machines there hold only 7 kg.
To tell you the truth, I already washed the blanket there and made a big watery mess on the floor cuz the blanket was too big.
Would the dry cleaners wash it normally though? I don't want to pay a big bill for something that doesn't need to be dry cleaned.
This is for next time I need to wash it.

Our neighborhood dry cleaners actually washed our futon. It costed about 3000 yen. If yours can't do it, they might be able to send it out somewhere to get it done.

Normally, you only wash the cover of the kotatsu futon. The kotatsu futon itself is supposed to be dried under the sun on a nice sunny day (like futon for sleeping). By drying under the sun, germs and mites in futon will die, and the air will get rid of a large part of the smell.

But since unlike sleeping futon, we don't mind if kotatsu futon becomes less fluffy, do we. So I just throw it in my washing machine, whenever I need to (like when I spill something over it!).

The problem however is whether or not your waching machine can take it. A lot of the smaller or older machines cannot. Take a look at your operating manual carefully.

There are also "washable" kotatsu futon (as well as sleeping futon) available, so if anyone is planning to buy a new one, it might be nice to keep that in mind.

Btw, I don't understand why you made a "big watery mess on the floor". When you wash something in the washing machine, I think you'd normally spin-dry it afterwards in the machine. Then the washed item will be safely dry enough to be carried to your window or garden to be finally dried crisp and fluffy under the sun.

Because the futon took up so much space in the machine that the machine just used it's normal amount of water... and when it began to spin, the water slushed out. Maybe if the machine could hole more... but then again it's a coin laundry.

I guess I have to say that you used the machine the wrong way...

Maybe the washing machine broke. It's not rocket science.