Low flow toilets aren't just old toilets that use less water. They are designed from the beginning to work with less water. The flush valves and sizes are different. The jets are different. The shapes are subtly different.

So while you could set up your old toilets to use less water, you will have a difficult time making them work with less water and you may have to flush more than once. You'd be better off purchasing new toilets with an older look. They do exist, and they can pay for themself over time.

Yes. Put bricks in the tank.
Renee

I have been studying which toilet to buy, and here is an article I found that explains how low-flows work. As the article explains, a low-flow toilet employs a different design.

Here is a link that might be useful: HGTV Low-Flow Toilet Article

An old toilet cannot be retrofitted..It is true that you can slightly reduce the water consumption in an old toilet by placing a brick in the tank, but the savings is only about 1 qt of water and often it will cause the toilet to not flush properly...

I am attaching two illustrations that I made. The first one will show the complete step by step process in how a toilet flushes...

The second illustrates the technical differences between a 3.5gpf toilet and a 1.6gpf toilet. As you can see from the illustration, you can not convert a standard bowl to a water saver.

Thanks, everyone. I was thinking of something like this, but it sounds like that's a no-go. I'm just curious about all these old 1950s ming green or Mamie pink toilets I've seen antique/retro shops selling, like this. Do people just buy and install them themselves on the quiet? Our contractor implied that the town wouldn't "let" us keep our older toilets.

Here is a link that might be useful: Old bath fixtures for sale

Beautiful. I suppose if you pulled permits for a big remodel you must put in new stuff- my dad just had to put in led can lights in a kitchen remodel.

Different towns probably have different permit processes.

If you're not getting permits, you can do anything you like :)
Renee