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Old 10-04-2014, 05:08 PM
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Grrr! Grrr! is offline
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Low flow toilets: If you raised the tank by two feet.

Wouldn't that help eliminate a lot of the clogs normally associated with low flow toilets?

(My theory being that the water in the tank would enter the bowl at a higher rate of velocity.)
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Old 10-04-2014, 05:14 PM
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beowulff beowulff is online now
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Modern low-water-usage toilets flush as well (or better) than the old kind.
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Old 10-04-2014, 07:02 PM
enipla enipla is offline
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Originally Posted by beowulff View Post
Modern low-water-usage toilets flush as well (or better) than the old kind.
I have to agree with you here. But, If someone has one of the old low-flow toilets. Well, they sucked. And not in a good way.
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Old 10-04-2014, 11:16 PM
boytyperanma boytyperanma is offline
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Siphoning is a much more important factor in a toilets ability to flush. Raising the tank higher would have minimal effect on the siphon. Current generation of toilets are well designed taking into account the amount of water available per flush.

The original low flow toilets simply took a standard high flow toilet and put a smaller tank on them. This resulted in a generation of poorly designed toilets whose ability to siphon was dependent on more water than the tanks provided. They were terrible. That generation is what everyone has stuck in their heads when they believe low flow toilets are bad. The new ones work just fine and don't need new concepts like raising the tank applied.
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Old 10-04-2014, 11:51 PM
Snnipe 70E Snnipe 70E is offline
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Originally Posted by boytyperanma View Post
Siphoning is a much more important factor in a toilets ability to flush. Raising the tank higher would have minimal effect on the siphon. Current generation of toilets are well designed taking into account the amount of water available per flush.

The original low flow toilets simply took a standard high flow toilet and put a smaller tank on them. This resulted in a generation of poorly designed toilets whose ability to siphon was dependent on more water than the tanks provided. They were terrible. That generation is what everyone has stuck in their heads when they believe low flow toilets are bad. The new ones work just fine and don't need new concepts like raising the tank applied.
Agreed. Raising the tank would have little or no effect.
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Old 10-05-2014, 02:43 AM
chappachula chappachula is offline
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So what is the difference in the physics of old-fashioned low flow toilets and the newer ones?
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Old 10-05-2014, 07:42 AM
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So what is the difference in the physics of old-fashioned low flow toilets and the newer ones?
Much larger flush valves, for one.
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Old 10-05-2014, 08:17 AM
Batfish Batfish is offline
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Modern low-water-usage toilets flush as well (or better) than the old kind.
Yeah, maybe. Except for that shit smear on the bowl because there's very little water in it.
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Old 10-05-2014, 09:16 AM
pulykamell pulykamell is offline
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Originally Posted by beowulff View Post
Much larger flush valves, for one.
Yeah, I just replaced my old low flow toilet that was continually getting clogged with a modern one and was astounded at the difference. The old one had a smaller flush valve and the way it would flush was in the familiar flush swirl. So if you're flushing, you know how the bowl fills up, swirls, swirls, then (hopefully) all goes down the drain with a gurgle? I think the whole process would take about five to seven seconds from flush to evacuation of contents. The new one I have, the water just drops straight down without a swirl and is through the pipes in about a second. Haven't had a single clog on it yet.
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Old 10-05-2014, 01:20 PM
Snnipe 70E Snnipe 70E is offline
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Old-fill the bowl to start a syphon. Bowl fill with water through holes around top ring and a 1/2" hole in bottom of the exit throat. As bowl empties pulls everything with the water.

New- 1" hole in bottom of exit throat. When handle is pushed down Tank empties in just a second or less. All the water goes through the 1' hole. Velocity carries the small amount of water and solids in the bowl out the back of the bowl and down the drain. Flapper closes and as tank refills some water is diverted to refill bowl.
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Old 10-05-2014, 03:22 PM
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Maybe it varies by brand. I got a new toilet last year and it clogs. I wouldn't say it was frequent, but considering that the old ones NEVER clog....
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Old 10-05-2014, 04:14 PM
LSLGuy LSLGuy is offline
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A lot of cheap toilets, low flow or even those from the pre-low-flow era, have small passages through the S-bend. Anything larger in diameter than a golf ball barely fits.

Better toilets have much larger throats. They can almost pass a softball.

You can see how one would clog much more readily than the other.
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Old 09-09-2018, 08:28 PM
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Originally Posted by Snnipe 70E View Post
Old-fill the bowl to start a syphon.
The "syphon" bowls were an American thing. And I'm not sure how "old" they were - I don't actually remember them from the 50's, but I was young then. Our old Aus toilet (on an English model) had a cistern at about 6'. And it did push down and through. They were replaced with a lower cistern that relied on higher volume. And then we got low-flow-that-doesn't-work-very-well.
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Old 09-10-2018, 12:07 AM
harmonicamoon harmonicamoon is online now
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I remember seeing, back in the old days, the tank was close to the ceiling. And you pulled a chain to send the water down.
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Old 09-10-2018, 02:51 AM
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Originally Posted by harmonicamoon View Post
I remember seeing, back in the old days, the tank was close to the ceiling. And you pulled a chain to send the water down.
I replaced the one in our house soon after we moved in. Like many of its breed, there was a trick to get it to work. As I recall, one had to pull fairly gently (to prime it?) and then a vigorous but smooth pull all the way and hold.
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Old 09-10-2018, 05:58 AM
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Originally Posted by harmonicamoon View Post
I remember seeing, back in the old days, the tank was close to the ceiling. And you pulled a chain to send the water down.
My father had one years ago. Most of the year you had to put a towel over your head and back when sitting on the commode or risk having water drip on you from the tank.
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Old 09-10-2018, 06:00 AM
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When my brother bought his current home in Michigan he was unhappy with his toilets. He couldn't purchase what he wanted legally in Michigan, so he rented a truck and drove to Canada, where he purchased five Michigan-illegal toilets. He then hired a plumber to install them on the sly, paying him in cash.
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Old 09-10-2018, 06:21 AM
Bijou Drains Bijou Drains is online now
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Originally Posted by harmonicamoon View Post
I remember seeing, back in the old days, the tank was close to the ceiling. And you pulled a chain to send the water down.
if you want to see an example of this , watch the Godfather movie. that's the first time I saw one of those
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Old 09-10-2018, 07:54 AM
kanicbird kanicbird is offline
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Originally Posted by Batfish View Post
Yeah, maybe. Except for that shit smear on the bowl because there's very little water in it.

I noticed this with our dual flush toilets, which have the advantage of a #2 flush of 1.8 g instead of the 1.2 g / flush. They didn't stay clean. However I moved the water level slightly higher then the 'max' level and that made a big difference in the bowl being clean. Not as good as the swirl action of days go by but does take care of most of it.
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Old 09-10-2018, 08:16 AM
jjakucyk jjakucyk is offline
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Originally Posted by Hermitian View Post
Maybe it varies by brand. I got a new toilet last year and it clogs. I wouldn't say it was frequent, but considering that the old ones NEVER clog....
I have an old high-flow from the 1980s that clogs constantly, there's the anecdote to cancel out yours.

Anyway, as most have already explained, diverting most of the water away from the rim to the "jet assist" at the bottom of the bowl is one of the big factors, along with the increase in the size of the flapper, allowing the water from the tank to be dumped very quickly. Another thing that was done was to fully glaze the trapway after the bowl. In older toilets it would be just bare porcelain with a rough sandy texture beyond where you could see it. By glazing it that makes everything slide along better. Raising the tank or increasing the water pressure wouldn't have much impact on this.

These are all still technically siphon toilets. I don't think that's ever changed. Washdown toilets, which are popular in Australia and parts of Europe, don't have the jet assist and pour all their water out of the rim. They do it faster so it basically forces the contents of the bowl out the bottom. It seems to use more water, but that could be just because you see it all. I don't know that it's really more effective either, just maybe better in some ways and worse in others.
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Old 09-10-2018, 08:59 AM
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I believe the way manufactures are handling the need for a more powerful flush today beyond what is 'normal' is to go pressure assist, not a higher tank height. Though that may be going away as modern designs do work well without the extra hardware that once was needed to get a low volume flush to work.

But I've seen some that also have a self cleaning mode where some form of cleaner is added. This takes care of the above mentioned smearing issue that most low flow ones have (as opposed to the old 'swirl' ones)
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Old 09-10-2018, 09:11 AM
jjakucyk jjakucyk is offline
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I see pressure-assist toilets (with a separate sealed plastic tank inside the porcelain tank used to store up pressure from the water supply without needing a larger pipe like in typical commercial flush-valve fixtures) in light commercial/office applications. I haven't come across one in residential though because they're quite loud. They do seem to work pretty well.
  #23  
Old 09-10-2018, 10:12 AM
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The water will come down faster, yes, but as the velocity of a fluid increases, its pressure decreases (see Bernoulli). You can also see if you pour a stream of water from a pitcher onto the ground that as the speed of the falling fluid increases, the stream thins out. In your scenario the water would enter the bowl at a higher velocity, but at a lower rate of volume/time.
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  #24  
Old 09-10-2018, 02:11 PM
Hari Seldon Hari Seldon is offline
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I have a new toilet with two operating modes. If you simply push the handle down and release it, only about 1/3 of the tank empties. If you need more than that, you have to hold the handle for ten seconds or so. Or just 5 if you need only some more but not the whole flush. The plumber who installed it didn't explain that to me until after I had a real clog that was very hard to plunge away until I also used a big flush.
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Old 09-10-2018, 04:29 PM
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Originally Posted by bob++ View Post
I replaced the one in our house soon after we moved in. Like many of its breed, there was a trick to get it to work. As I recall, one had to pull fairly gently (to prime it?) and then a vigorous but smooth pull all the way and hold.
They used a siphon (rather than a valve) in the cistern. The characteristic mode of failure (and reason most got replaced), was that the 'pump' action which primed the siphon failed due to wear and corrosion. So you'd stand there repeatedly pulling on the chain, softer, harder, slower, faster, trying to get it to flush.
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Old 09-10-2018, 04:35 PM
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Originally Posted by CookingWithGas View Post
The water will come down faster, yes, but as the velocity of a fluid increases, its pressure decreases (see Bernoulli). You can also see if you pour a stream of water from a pitcher onto the ground that as the speed of the falling fluid increases, the stream thins out. In your scenario the water would enter the bowl at a higher velocity, but at a lower rate of volume/time.
Let me re-describe that. The actual volume/time is set by the flow restriction, not the length of fall. You don't actually get /less/ volume just because the cross-section gets thinner. And Bernoulli decreases the static pressure in proportion to the /increase/ in the dynamic pressure. And the static pressure with a high cistern is greater. So at the bottom, the bowl, the you get a high-pressure flow.
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