Reservoir Tank - Gravity Feed

[Bubbles Galore]

I have an 80 gallon tank that I've filled up and am trying to gravity feed to my IBA tank using 1" tubing. When the IBA tank is calling for water and the valve opens, it's not drawing the water in like I assumed it would. What am I missing? Any and all input is appreciated, I spent way too much time on this project to have it not work for some silly reason. Help!

 

[Jim L.]

The inlet port on my Cat 3535 is 1.5". All the plumbing from holding tank to pump is also 1.5".

 

[Waxman]

Is the top tank properly vented?

 

[Bubbles Galore]

The inlet port on my Cat 3535 is 1.5". All the plumbing from holding tank to pump is also 1.5".

Hi Jim, mine is the same way. My main pump reservoir has been fed with a 1" line since the install and I haven't had any issues with the feed itself. I figured an 80 gallon tank set above the pump stand would build up enough head pressure to feed the tank when the system called for water via the solenoid. Am I mistaken?

 

[Bubbles Galore]

Is the top tank properly vented?

Not quite sure what you mean, but I don't even have the lid on it as of yet.

 

[Jim L.]

I’m thinking that a 1” gravity feed is too slow to keep up with the 30-35 gpm of an auto pump. My auto originally had a 50 gal. holding tank that was fed by a 1” city water line. Most days the tank would fill slightly quicker than the pump would consume it. On days when city pressure was not up to standard, my pump would starve by the end of a wash. I fixed this by replacing the 50 gal. tank with a 500 gal. and changing the plumbing leading to the pump stand to 2”.

 

[cantbreak80]

snipped from Cat Manual

"Line size must be a minimum of one size larger than the pump inlet fitting. Avoid
tees, 90 degree elbows or valves in the inlet line of the pump to reduce the risk of
flow restriction and cavitation."

 

[Bubbles Galore]

snipped from Cat Manual

"Line size must be a minimum of one size larger than the pump inlet fitting. Avoid
tees, 90 degree elbows or valves in the inlet line of the pump to reduce the risk of flow restriction and cavitation."

The way I'm reading that, it lends itself to some interpretation. Since I'm feeding the tank and not the pump directly, could I plumb in a 1.5" pvc line to the solenoid and get enough head pressure to feed the tank as it sits?

 

[waright]

If you are using a solenoid on the 1" line, perhaps the solenoid is your restriction. Some solenoids need more pressure to fully open. You could just put a float valve in the tank and not use a solenoid

 

[tobaccofarmer]

The solenoid is definetly your problem, most need atleast 5lbs of pressure behind them to open properly. One solution I have used in the past is a accuated ball valve which allows full flow without back pressure, another is a float valve like a casa 1inch which also doesnt require any back pressure for flow. The casa float is simple and we all know simple usually outways anything else. I also use hudson float valves but they also require backpressure and would not work in a gravity feed situation either!

 

[Indiana Wash]

Bubbles,

I had the same issue. I set up a reclaim for my RO reject. I put a 215 gallon tank above the auto's with 2" pvc gravity feeding the whole way down. At the end, I went with 1" float valves.

Guess what, that was not enough pressure to actuate my valve. Even with the float telling the valve to open, there was not enough pressure behind it.

I switched to 2" BOB valves. They work perfectly. I did not think they would since the float is the only thing that holds them closed. They are not 2 stage valves but just have a plunger that closes the water off when the float comes up. These are the ones I used.

http://www.grainger.com/Grainger/Float-Valve-6AMA6?Pid=search

I did have to cut the float rod down a little but it did not affect it.

 

[pitzerwm]

I believe that you get .5 lb pressure per foot of height.

 

[Indiana Wash]

I believe that you get .5 lb pressure per foot of height.

So a 200 gallon tank at 10 feet feeding through a 2" line with a 1" float valve has te same pressure as a 1 gallon tank at 10 feet feeding through a 1/4" line with a 1" float valve? I think there has to be more to it than that, but I am not a plumber or physicist.

 

[robtl]

The solenoid is definetly your problem, most need atleast 5lbs of pressure behind them to open properly. One solution I have used in the past is a accuated ball valve which allows full flow without back pressure, another is a float valve like a casa 1inch which also doesnt require any back pressure for flow. The casa float is simple and we all know simple usually outways anything else. I also use hudson float valves but they also require backpressure and would not work in a gravity feed situation either!

On our rinse tank there were two holes at the top where the fill valve was, we ran a 2" pvc header with two 2x2x1" tees and added two Bobs 3/4' float valves and they keep up fairly well.

 

[MEP001]

Even if a solenoid can open with the pressure from an 80 gallon tank behind it, the path through the solenoid is going to restrict a lot of the flow because it's not straight through. You should definitely use at lease one 1" direct-acting float valve and mount it as high in the auto tank as possible. Ideally it will fill the tank above the existing float valve so you can get as much water used and refilled as possible.

 

[Indiana Wash]

Even if a solenoid can open with the pressure from an 80 gallon tank behind it, the path through the solenoid is going to restrict a lot of the flow because it's not straight through. You should definitely use at lease one 1" direct-acting float valve and mount it as high in the auto tank as possible. Ideally it will fill the tank above the existing float valve so you can get as much water used and refilled as possible.

Yes, what he said. That is what I do. However, I use a 2" direct acting float valve and fill the tank above the existing float valve so I use as much RO reject as possible.

 

[JIMT]

I believe that you get .5 lb pressure per foot of height.

According to my Google search one Cubic inch of water weighs 0.036127 pounds so 12 inches of height would give .036127 times 12 inches equals .433 psi.
JIMT

 

[pitzerwm]

Jim T, I wouldn't go to the bank with that, but that is close to .5