View Full Version : 1.28 gpf design / engineering question

02-14-2008, 11:32 AM
I was speaking with a toilet dealer about their 1.28 gpf offerings and they said that they are the same exact bowl/tank as the 1.6 gpf but have just been regulated to only use 1.28 gpf. My questions is are there any models that have been specifically engineered for 1.28 gpf and are not just a regulated 1.6 model?

Ian Gills
02-14-2008, 01:46 PM
I asked Terry this once and he said that smaller tanks would look funny, so they do not do it like that. And there was also a flush issue too, something to do with height of water and power of the flush.

02-14-2008, 05:01 PM
regulated to only use 1.28 gpf

All of the 1.6 tanks have been regulated to use 1.6 gpf
The 1.28 tanks have qucker flappers or flush valves.

Some lines are using the same bowl for both.
Right now I'm using the Drake E bowl and E tank in the main bath.
I have the S Ultramax downstairs.
I'm not seeing much difference.

The new bowls I'm seeing, are marked as "1.6 gpf or less".
I have one, it seems to be working.

02-15-2008, 10:31 AM
Terry, just so I understand the only difference between a 1.28 and a 1.6 gpf toilet is only in how much water flows through the system?

I was thinking that if you send 20% less water into a system (bowl) you would want to adjust the system appropriately so I was wondering if any manufacturer had made total system changes to match the 20% less flow.

02-15-2008, 11:18 AM
Are the 1.28 and 1.6 gpf bowls different?

02-15-2008, 02:24 PM
I haven't talked to their engineers on it, but it seems that the 1.28 I have, is a little quicker than the 1.6, and doesn't overfill the bowl as much.

Plumbers will know what I'm talking about here.
Many toilets have an overflow tube where the water from the fill valve goes. This refills the bowl after it's flushed.
Water keeps filling the bowl, until the water in the tank reaches the shutoff level. With most bowls, that means, that not only is the bowl filled back up, it's filled and filled, wasting much water down the drain.
The engineering part I see is,
1) Using just enough for the flush
2) And preventing the over filling of the bowl during refill.

02-15-2008, 03:10 PM
Terry, thank you for the detailed explanation. That is what I needed.

02-15-2008, 04:20 PM
As far as the specs that California is about to start phasing in, a toilet has to flush an "average" of 1.28. If the toilet is a dual flusher, I believe the average is calculated on 3 or 4 number ones per number two. SO it can actually be a regular 1.6 GPF for the normal flush, as long as it has a button for a #1 flush of about 1/2 gallon or so.