I have to add to this. I had the one enema when I was 9 and hated it. Then for years hated anyone touching me back there. Then I started dating a girl online who lived in a different state. She ended up moving in with me. We were together for two+ years. But pretty close to the start she let me know that she loved anything anal. I didn't mind doing anything to her. But not to me.
After sex one night we talked and I told her what I thought and how I would freak out if someone ever felt anything in me. She asked if I had ever felt anything in her. I said no. She said that is because she does enemas. I figured she must have been sneaking them. But she asked if I would help her. I did and after three weeks of watching her have major orgasms, I got up the nerve to try.
It was a slow process and took weeks before I could even take a full bag. After a few months, we were doing enemas and expelling in the potty.
I guess we had done four enemas each in a series, maybe three so we were pretty clear. We both got in the tub and started playing again like we did a lot. We started talking about how much we thought we could hold. As for me, I am multi-orgasmic. Just be careful of the magic button until it is time. I think that is where my ex screwed up. He would just go straight for the clit when doing anything with me. He never gave me enemas. No way.
This girl who started me on them was a while after him. Anyway, orgasms get me through cramps and that is the only way I can take a full bag. She asked if I thought I could take two bags. She made it sort of like a dare to try bet. I said okay. So she filled the bag and started giving it to me while she was rubbing just above my clit. Usually, after the second enema in a series like on the third enema I don't have any cramps, and if I do they are slight. So that bag was almost empty and she started the water. As soon as I finished the first bag she clamped it and filled the bag again real fast. Then unclamped it. About halfway through that bag, I started to cramp and it was as if I could not hold it. She started rubbing my clit to try and help me through it but that was all I could take and it started coming out. I'm glad I was in the tub. As soon as I bent to kneel to get up to the potty it gushed out. But that we decided was three quarts.
So I did not have much experience with enemas. That was the only time I ever attempted that. She did it later and held about the same. But she had enemas her whole life. I read about people saying they do their regular four quarts or more and I don't know about that. Maybe four quarts but some of the claims are crazy. I don't know if it has to do with size or experience.