Installation was a breeze. I spent 10 minutes skimming over the instructions, and probably 30 minutes for installation and adjustment. Adjustment takes the longest amount of time, because you have to keep flushing the toilet and waiting for it to refill before testing the next adjustment. I don't understand why some reviewers said that it took them so long to read the instructions and install the unit. I have lots of experience with replacing toilet fill valves and such, so maybe it was easier for me than it was for some people. As one reviewer mentioned, you have to make sure that you get the most current version of this product. I chose the lowest priced option with free Prime shipping, and the product came from the seller named "Innovative Retail Market". I received the old version of the product from this seller, so I cannot recommend them. Fluid Master happily replaced it with the newer model 550DFRK-1 (the -1 indicates that it is the newer version). I used my water meter to measure how much water my toilet used before I installed this unit. It used 1.9 gallons per flush (gpf). This is slightly more than the rated 1.6gpf printed on the toilet. I suspect that the difference has to do with the fact that the old fill valve over-filled the bowl a little, which allows more water to go down the drain. When I installed the unit and new fill valve, I set the water level in the tank at the same height where it was before. This resulted in unsatisfactory results. Even with both adjustment dials turned to MAX, the toilet would not flush. So, I adjusted the new fill valve to fill the tank to the "max fill" line, which is engraved into the inside of the tank. This allowed me to adjust the dials to allow a complete flush with both liquid ("half flush") and solid ("full flush") waste. The liquid adjustment was easy... if three sheets of toilet paper go down, the adjustment is correct. The solid adjustment took an extra day or two of using the toilet. I had to increase the solid adjustment once, in order to ensure a complete flush. I guess that was an extra-high-fiber day. LOL I eat lots of vegetables. I have been using it now for almost a week, and it works perfectly. As they say, the proof is in the pudding. So, I wanted to measure the water savings. Your results will vary, because each model of toilet has a different flush performance. My toilets are not the best performing water-saving toilets I've ever owned, but I'm a renter now... and I think my landlord would probably get upset if I replaced the whole toilet! With my current settings, a "full flush" uses 1.6 gallons, exactly what the toilet is rated to use. This is a savings of 0.3gpf, compared to what the toilet used previously. A "half flush" uses 1.3 gallons. While this isn't a huge difference (certainly not "half"), it is something... and would probably be better with a toilet which has a better flush performance score (yes, that's actually a thing). I used to own my home, and I installed toilets which had a flush performance of 10.0 (the highest possible). I think that those toilets would probably flush liquids with far less than 1.3 gallons. Unfortunately, I never installed a duo-flush valve in them. At my new place of residence, the cost of water is double what it was at my old place... so I'm looking at ways to save water. So... the important question is: "Is it worth the money to buy this device?" ... I estimate that this unit will save me about 50 gallons per person, per month. At my current cost of water, that's about $1.00 per person, per month. Since I only paid $18.99 for this thing, it will pay for itself in: 19 months in a 1-person household 9.5 months in a 2-person household 6.33 months in a 3-person household 4.75 months in a 4-person household etcetera ... Of course, if you buy two or three of them for all of the toilets in your house, you need to double or triple the number of months I mentioned above. In my case, yes... it was worth the money. I would have liked to see a lower gpf for liquid flushes, but... overall.. I'm satisfied. Oh, I should mention something else. Some reviewers complained that the handle seemed flimsy. I disagree. I think it is sturdy enough. Maybe they didn't tighten it enough, allowing it to wobble in the hole?
