My autofill

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WhoDat?

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Dec 16, 2011
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I just built my 2nd pool! I followed TFP methods for maintaining my first pool and had zero issues and plan to do it again! You guys are great!

Ok so I decided on this pool to do an auto fill... I didn't like the idea of having another opening in the cement so my idea was to have the autofill far away from the pool.. near the pumps... so basically what I did was add an extra return in the pool wall... connected to 1.5 inch piping... and ran it about 1.5 ft lower than the pool water level over to the pump pad.... connected the pipe to a round water tank that would hold the float valve... when filling the pool for the first time as the water level got to the pipe it started to fill my water tank as well... when the pool was finished filling all water was level...

The problem is that when I add water to the tank... it doesn't raise the water in the pool... if I pump water out of the tank... it immediately fills the tank back up with pool water.. as expected... but why wouldn't it work the other way? If I add water to the tank it just fills up and stays full, and is higher than the pool water... why wouldn't it level the water out? I would guess that the pressure in the pool is higher but it shouldn't matter when dealing with water level...
What am I missing?
 
There is no check valves... just straight piping and a couple elbows... the water remains level in the tank... if I pump water out the tank.. it gets refilled by the pool to the same level... if I add water to the tank.. it just fills the tank and keeps it full.... as far as air... I guess it could possibly have air in the line... but the return jet is obviously under water... and the connection of the line to the tank is also underwater in the tank...
The tank is not pressurized or anything like that...
 
My best guess is that the volume of the pool is putting enough backpressure on that pipe to prevent the flow inward. But that defies pretty much everything I've ever seen about siphon effects, so I'm really not sure. Hopefully someone more experienced with plumbing has a good idea! Interesting problem, though; looking forward to see why this is happening.
 
WhoDat? said:
There is no check valves... just straight piping and a couple elbows... the water remains level in the tank... if I pump water out the tank.. it gets refilled by the pool to the same level... if I add water to the tank.. it just fills the tank and keeps it full.... as far as air... I guess it could possibly have air in the line... but the return jet is obviously under water... and the connection of the line to the tank is also underwater in the tank...
The tank is not pressurized or anything like that...
Click to expand...

DrHarris actually has an EXCELLENT question there - is the tank open at the top, or does it otherwise have ventilation to allow the air pressure in the unfilled portion of the tank to equalize when it's in use?
 
Possibly... I thought maybe I should have added the return higher in the wall.... it's about midway up the 3ft walls.. I put it even with the others... maybe there would be less back pressure if it were higher up the wall??? I don't know...

- - - Updated - - -

triptyx said:
DrHarris actually has an EXCELLENT question there - is the tank open at the top, or does it otherwise have ventilation to allow the air pressure in the unfilled portion of the tank to equalize when it's in use?
Click to expand...

The tank is open at the top.... there would be no way for any type of pressure... unless there's air trapped in lines somehow...
 
WhoDat? said:
There is no check valves... just straight piping and a couple elbows... the water remains level in the tank... if I pump water out the tank.. it gets refilled by the pool to the same level... if I add water to the tank.. it just fills the tank and keeps it full.... as far as air... I guess it could possibly have air in the line... but the return jet is obviously under water... and the connection of the line to the tank is also underwater in the tank...
The tank is not pressurized or anything like that...
Click to expand...

Edit: You answered my question with your last reply

But my next question is how are you treating the water in the tank? If you dont have any leaks in your pool you shouldnt be losing much water. The water in the tank should just sit there for the most part. Stagnant water is a great breeding ground for algae unless it is treated.
 
You said float valve, what is it, is it not adjusted correctly? With your tank level higher then the pool the float keeps it from over flowing the pool, instead it's just shut most likely. It might be installed backwards, if you can move the float push it all the way down and see if it fills the poil
 
Ok i might not have been clear... this is a new build..... the float valve and everything is not even functional right now as far as the float valve etc... I am testing out the system... like I said it filled the tank to the same level as the pool... the pool water level was still a bit low when I initially filled it.. so to test out the flow from my autofill I put a water hose in the tank thinking it would fill a bit and then start flowing into the pool and raise the pool water once the water in the tank raised.... but the tank just filled up and started over flowing... thinking that maybe the water hose was just putting water in too fast I turned it off hoping it would level off... it never did... tank stayed full... so thinking maybe the line was clogged I pumped the water out of the tank.... as soon as it got below the level of the pool water began to flow into the tank and leveled off again... again I tried adding water to the tank to simulate if the float valve would add water and again it just filled up...
 

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I'm completely baffled - everything I know says that it should equalize the pressure between the tank and the pool both ways.

Is the pipe out to the pool rigid pvc and about the same size as the regular pool returns?
 
I think it has to be air, but can't explain why it works one direction but not the other, unless air is being overcome by pressure-related forces, not a true siphon. Do you have a hose long/flexible enough to go from the tank all the way into the pool? You could put it in all the way, and gradually remove it so that it fills the pipes in a way that forces the air out. It might even work to run the hose just sealed to the pipe entering the tank so that it forces air out the other end, instead of running it all the way through.

But that has me thinking... even once you solve this, would typical outgassing from pool chemistry be enough to eventually prevent the siphon from being maintained? You might would have to put some sort of bleeder valve in the middle of the pipes. Kind of like a siphon hose with a check valve in the middle for sucking the air out. But again, not an expert here so I don't know if that is even a potential problem or not. I just know lots of plumbing systems have little relief valves for gases, so this might need the same if you're trying to rely on the siphon effect.
 
If water only flows one direction there has to be a check valve installed backwards. I've used clear tubing over long distances as a water level, it is always accurate. Try running a fish tape down the pipe from the tank. If you hit something that you can't get through it is most likely the check valve. Try it from the pool, you should be able to push through the check valve. It will be difficult to get the fish tape back out and you will most likely ruin the check valve.
 
Lol... I am 10000000% sure there is no check valve... I installed the entire pool... including the autofill... 1.5" return.... connected to a few 90's.... connected to about 20' of 1.5" pipe.... connected to the tank... that's it.... that's why I don't understand the issue!
 
I agree, must be some sort of air purge issue. I've had good success using the suction from my pool vac disconnected from the navigator and held against the wall to clear the line.

But if you get too aggressive you can add air by running the tank empty. The only other thing I can think of is you have an issue with the pipe doing a whoop de do in the ground (I know super techy). Being that it changes level too many times in the ground and you are hydro locking the liquid in the pipe and the tank doesn't have enough volume to force the flow.
 

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