Supplying Water to Toilet from Gravity Feed Tanks

[micky]

Right. The water from a runaway toilet valve just runs into the toilet bowl and out the rear of it.

[nestork]

No, it really is the water pressure. Otherwise, why wouldn't your washing machine start filling up with water the instant you unplugged it?

I think you'd get a lot better performance out of that fill valve if you replaced the rubber diaphragm in it. I have seen toilets do that before, but that was before I knew anything about plumbing. Still I would try replacing the diaphragm in that fill valve and see if that helps.

If you believe the closure is caused by the water level in the tank raising the float, then wouldn't it make sense for flush valves to have a large float at the end of a long float arm to generate the maximum closure force. Why, for example, would designers make a fill valve with very short float arms, such as in the fill valve below:

[image:

And, wouldn't it make sense that a fill valve like the one above wouldn't work nearly as well as something like this:

[image:

In fact, you don't need much force to push a plug into or out of a rubber diaphragm, and so there's no real advantage in having a large float and a long float arm. If it was the buoyancy force of the float that shut off the water flow, then EVERY toilet fill valve would have a float the size of a large pumpkin on the end of a two foot long float arm because that's what would work best.

[Stormin Mormon]

Fortunately, yes, the excess water goes down the drain.

Thanks for the explanation.

Wouldn't the overflow tube shuttle the water into the bowl where it's own weight would override the trap preventing the "flood" that you speak off?

Most of us have experienced toilet valves that have not shut off but very few of us have experienced flooded houses due to that malfunction.

[Stormin Mormon]

No, it really is the water pressure. Otherwise, why wouldn't your washing machine start filling up with water the instant you unplugged it?

[micky]

I havent' done it, but it would fill fine. The part of the spin cycle where the water sprays (to rinse away the left over suds) would not work right in the machine I have. The water wouldn't have enough pressure to spray and would just wet the clothes again, a little.

[Jon Danniken]

Excellent description, thanks Nestork. I ran into this problem once when trying to tie a drip irrigation system into a rain barrel, as most of the water timers relied on high pressure to open.

Fortunately I found an old rain-bird unit that used a ball valve, which, despite needing a lot more energy, worked with the low pressure system (and that is one of the benefits of the high pressure one; they can work on a 9V battery just fine instead of the 4-C cells I needed with the ball valve unit.

Jon

[Stormin Mormon]

Question: Would a washing machine valve flow water (like a toilet valve) if the supply pressure were low, from a cistern? Does a washing machine valve require water pressure to close, like toilet valves in the original post?

I havent' done it, but it would fill fine. The part of the spin cycle where the water sprays (to rinse away the left over suds) would not work right in the machine I have. The water wouldn't have enough pressure to spray and would just wet the clothes again, a little.

[jamesgang]

I'm not sure that is true. Some devices like washers with mechanically tim ed cycles do not stop the timer until the water is full. Rather they have enough time in the cycle to permit it to fill and the fill is then shut off by a level sensor. In other words the timer keeps on ticking while it's f illing. If the fill takes too long the cycle will pass.

[jamesgang]

Then learn how to stop top posting.

[bud--]

I agree it is real common.

Is there a name for that type of mechanism?

[micky]

Just what I would have said.

[micky]

I could test this by turning the water off mid-fill, but that would only show how my one model was working, so I'm not going to bother.

I could also look at the diagram to see if the level switch interrupts the power to the timer motor, but the diagram is on the back of the washing machine, inside the removeable panel iirc. (My machine is 34 years old so it doesn't have a front that comes off. )

I hope I remember to look next time I have the panel off.

I also don't have much of a feel for how fast the machine would fill from a cistern, and it depends a lot on how high up the cistern is. On the roof of a one-story house, two stories, my summer place in Newport that is 6 stories tall?

[micky]

Yes, but at a low rate.

No, washing machine valves close when there is no power applied to them. They have a spring, and it's probably pretty strong given the thud that can sound through all the (cold water?) pipes in the house when the valve closes suddenly.

When we asked you to stop top-posting, you ignored us.

[nestork]

I think it's just called a "diaphragm valve". There are mechanical diaphragm valves, like on a toilet tank ballcock, and electrical diaphragm valves, like on a washing machine's water mixing valve.

[nestork]

It's more correct to say that water mixing valves OPEN when the hot or cold solenoiods in them are energized.

Back when they used to sell overhaul kits for washing machine water mixing valves, I overhauled the water mixing valve on my main floor washer. The hot and cold springs that push the plug back into the diaphragm when the coil is de-energized aren't any bigger or stronger than the springs you find in a typical ball point pen.

This image explains how the water mixing valve in a washer works fairly well:

[image:

Water comes in through the hoses and filtration screens on the right hand side.

The rubber diaphragm rests on a plastic seat. Water flows through that seat to get into the washing machine wash basket.

The water pressure is the same on both sides of the diapragm, but the area occupied by the seat reduces the area over which that pressure is applied on the far side of the diaphragm.

So, as long as the machine is off, the pressure equalizes on both sides of the diaphragm, but since force = pressure X area, there's a net force pushing the diaphragm down tightly onto the seat so that water can't flow into the washer.

When someone starts the washer, the hot, cold or both hot and cold solenoids are energized. This pulls the brass plated iron plug out of the hole in the middle of the rubber diapragm. When that happens, the pressure on the large area side of the diaphragm is released and the city water supply pressure on the small area side of the diaphragm pushes the diaphragm off it's seat. Water then flows under the diaphragm into the washing machine.

When the pressure switch in the washing machine senses that the washer is full, it stops the flow of electrical power to the hot and cold solenoids so that they are no longer pulling the brass coated iron plug in. The spring then pushes the brass coated iron plug out so that it covers the hole in the middle of the rubber diaphragm.

The water pressure then equalizes on both sides of the rubber diaphragm, and because the area of the seat reduces the area exposed to that pressure on one side of the diaphragm, there's a net force pushing the diaphragm down onto the seat so that water flow into the washer stops.

Here's what a water mixing valve for a washing machine typically looks like:

[image:

The two supply hoses you connect to your washer actually screw on to the mixing valve itself. Each solenoid is energized depending on whether you set the machine for a hot, cold or warm wash. The water enters at the two male threaded hose connections and leaves via the smaller tube on the opposite side of the valve.

Here's the water valve for a dish washer:

[image:

There's only one solenoid because you only supply hot water to your dish washer.

And, a toilet ballcock works exactly the same way, except that it uses the movement of the float to pull the plug out of the rubber diaphragm when you want water to flow into the tank, and push it back into the rubber diaphragm when you want to stop filling the toilet tank.

There you have it. The ugly truth about toilet ballcocks.

[clare]

Because a washing machine has a solenoid controlled valve - only open when powered.

I don't think you understand. I think he has turned the water control valve off to PROOVE that the fill valve works even with virtually no pressure.

Because they can.. And old (style) ones DID use a long lever - the new (style) ones are less trouble. (usually)

[clare]

Depends what you call "low pressure cistern water" If it has a pump it works fine.

[clare]

You are describing a piloted valve - which is quite common, but is NOT the only kind of water shutoff valve.

[micky]

This description has been bothering me for a day or so. Rather than the plug going in and out of the diaphragm, I think the plug is firmly fixed in the diaphragm, and the whole thing, the plug and the middle portion** of the diaphragm move back and forth as one unit when the water goes on and off. The valve itself is very close, on the wet side of the diaphragm. The plug goes out of and in the rest of the valve, depending on whether the water is flowing or not, and a flexible diaphragm is needed so that water won't come out of the top of the valve, like it would if there were just a hard piece with a hole just big enough for the plug. That would still leak but a diaphragm that hasn't ripped or cracked yet won't.

**The circumference of the diaphragm is immobile, in between the two pieces of the case, usually with screws every 30 or maybe 120 degrees around the circumference, holding the top, the diaphragm, and the bottom together.

I used a lot of words because I havent' found an adequate picture.

[ls99]

New guy here.

I read through this entire thread, since I am interested in the same as as the OP.

I note that some suggested a pump. In my situation for example, at a camp there is no electric except for occasional run of a generator. Solar power is available but very limited as well, only run a few LED lights.

The fundamental problem is filling a toilet with gravity at very low head, 3 foot above the tank top. I have tried ballcock as well as the newer short arm fill valves. Neither will shut off.

Using electric for pumping or valve control is out of the question. Current method is to turn on the manual valve to the toilet when posterior is on the seat, tank will mostly fill while on the throne. Flush. While washing hands leave manual valve on. When handwash is done turn off manual valve.

Rinse repeat.

So where does one find a fill valve which will function on a very low head water system?