DIY - Auto-refilling Seltzer Water Keg

[worxman02]

Hey gang,

So I've been using my spare keg to make seltzer since my wife loves flavored seltzer and I thought it was silly to buy bottles of seltzer when I have a perfectly good carbonation system sitting at home. It's also really nice during the summer and we go through 5 gallons pretty quickly. I'm getting tired of having to refill the keg every 2-3 weeks and shake it to carb it up faster, so I came up with a cunning plan that I wanted to run past the forum.

I've designed but not tested a constant filling system for my seltzer keg. Currently I have a carbon filter that I hookup to my faucet and run the output hose into the keg when it needs to be refilled. Well I wondered if I could just run the hose straight into the keg and it would refill the keg as the water level dropped. So I've come up with the following solution:

The above schematic demonstrates my idea. I'm filling up the keg through the gas in port instead of the liquid out so uncarbonated water cant go directly to the tap. So the cold water supply from the nearby sink goes into a Tee to split it into keg supply and faucet supply. That then goes into the filter which is not shown, but is located between the 2 compression fittings before the QD (which is a free dripless QD that I scored as a sample). the QD then goes into a check valve (to prevent gas from entering the water supply) and into a flare Tee that connects to the Gas QD. The gas in line connects to this Tee with another check valve to prevent any water going up the gas line, even though there is one at the manifold, I'm just being extra cautious.

I figure this will work because the water pressure is probably higher than the 30 psi that the keg is at so water will still flow into the keg. I haven't measured but I probably should measure the pressure after the filter before making all the effort to construct this system to find out it doesn't work.

What do you guys think? Am I crazy or a genius or a little of both? If I do get this working I'll be sure to post a build thread with pictures and results. I'm crossing my fingers for success! Now that I think about it, I might also ask some of the plumbing engineers that I work with and get their professional opinion on it.

View attachment Seltzer_Schematic_2014-05-15.pdf

 

[DrunkleJon]

Interesting. the googles tell me that normal household water pressure is ~40-70 PSI. The only worries I would have then would be they you would still have the balancing issue where you will only get ater filling the keg and no gas. I am thinking that for this purpose maybe using one of those see through PET kegs like the one here.
http://www.kegworks.com/5-gallon-pet-homebrew-keg-with-us-sankey-coupler-fitting-778-p178096
Then with minor modifications (just 2 valves, one on gas one on water) you can close off gas, open water, and bleed pressure off until the keg is full again. Then reverse your valves and check on it in a couple days to refill. It would be cool to see this working so please do update us as it goes.

 

[AnOldUR]

Love this idea. We always of seltzer on tap and go through the 5 gallon keg in a week during the summer. The fill and shake method I use to keep it flowing is a PITA.

 

[horseinmay]

Pretty cool. I'm an engineer with a water company, and we run our systems about 55-80 psi. It should work

 

[crane]

I like the idea and hope you can find a way to get it to work so I can implement it as well. I have a few questions/doubts about this design though. normally I have my gas set to 30 psi for seltzer water. If you hook up a water source of 50-80psi then the entire keg will rise to 50-80psi right? At that point the gas supply will be a lower pressure and you will no longer be able to carbonate the incoming water. Also your serving pressure will now be at 50-80psi instead of 30 psi. Can this issue be overcome by adding a pressure regulator to the water supply that drops the incoming water pressure to 30 psi?

 

[horseinmay]

The water coming in at higher pressure than 30 psi only means that you would not have to bleed the pressure in order to fill the keg. That is only true for the first bit of water. As it displaces the gas, pressure would equalize at the pressure of the incoming water, and then you would need to vent pressure in order to top it off.

Do you plan to operate this manually, or will there be a float switch, or some other way to automate the topping off of the keg? If manual, it looks good to go.

 

[DrunkleJon]

I think the original idea was a set and forget style solution where as water was poured out of the keg, an equal amount of water would fill the keg back up and then the gas would progressively dissolve to carbonate. The only way I see this as working fully automatically is if it were something more along the lines of the restaurant soda fountain machines method.

 

[Vetter]

If there is a constant water pressure of say 50 psi, pushing against the gas check valve of 30 psi. What will allow the gas check valve to open and add CO2 to the tank?

 

[DrunkleJon]

Exactly, I think you pretty much need a way to tell how much water to add to the keg and then just switch over from gas to water pressure then turn the water off when full. Check valves on both sides and some way to determine how high the water level is on the keg. Kinda like a sightglass or a see through keg.

 

[AnOldUR]

What about some kind of float like in a toilet? It could be set so the water only goes in when the level in the keg hits a set level. Say every time the 5 gallon keg hits 4 gallons, another gallon is added then the water shuts off. The question is, would one gallon of un-carbed water added to 4 gallons of carbed water have too much effect on the carb level? It would take some trial and error to find out the right amount to set the shut-off at.

 

[sandyeggoxj]

What about a prv on the water inlet so that you can balance it with the co2 pressure?

 

[crane]

What about a prv on the water inlet so that you can balance it with the co2 pressure?

That's kind of what I was thinking. If you could balance the pressures right, could you achieve a specific ratio of water and gas coming in as you pour a glass?

 

[worxman02]

I like the idea and hope you can find a way to get it to work so I can implement it as well. I have a few questions/doubts about this design though. normally I have my gas set to 30 psi for seltzer water. If you hook up a water source of 50-80psi then the entire keg will rise to 50-80psi right? At that point the gas supply will be a lower pressure and you will no longer be able to carbonate the incoming water. Also your serving pressure will now be at 50-80psi instead of 30 psi. Can this issue be overcome by adding a pressure regulator to the water supply that drops the incoming water pressure to 30 psi?

That's a good point. I kind of forgot about the water pressure affecting the keg pressure. I was simply thinking, "Oh hey, I know my water pressure is probably more than 30 psi, so it will overcome the CO2 pressure and fill the keg." I completely ignored the fact that the water will pressurize the keg to higher than the CO2 and then the gas wont flow. I wonder how much of a pressure drop the water filter that I am using has. I agree that dropping the water pressure down to 30 psi might make it work.

 

[worxman02]

The water coming in at higher pressure than 30 psi only means that you would not have to bleed the pressure in order to fill the keg. That is only true for the first bit of water. As it displaces the gas, pressure would equalize at the pressure of the incoming water, and then you would need to vent pressure in order to top it off.

Do you plan to operate this manually, or will there be a float switch, or some other way to automate the topping off of the keg? If manual, it looks good to go.

I was originally thinking it would just fill the keg as the water level dropped but I forgot about the effect of the higher water pressure on the gas in the keg. The idea was to have it automatically fill the keg as the level dropped, but I didn't want to get into complex valves and such. I was trying to keep it rather simple, but that might not work out.

 

[worxman02]

That's kind of what I was thinking. If you could balance the pressures right, could you achieve a specific ratio of water and gas coming in as you pour a glass?

That might work. How do the commercial carbonation systems work?

 

[Weezy]

Maybe a simple, inline water pressure regulator? Set the water pressure to equal the co2 pressure?

 

[worxman02]

That might work. How do the commercial carbonation systems work?

So according to wikipedia:

In many modern restaurants and drinking establishments, soda water is manufactured on-site using devices known as carbonators. Carbonators use mechanical pumps to pump water into a pressurized chamber where it is combined with CO
2 from pressurized tanks at approximately 100 psi (690 kPa). The pressurized, carbonated water then flows to taps or to mixing heads where it is mixed with flavorings as it is dispensed.

This seems like they are doing something similar but with pumps to increase the water pressure to an unknown pressure (probably at least a 100psi otherwise it wouldn't flow into the tank) to match the 100 psi of the CO2. I'm sure the tank doesn't get bleed when the pump fills it with water since that would be to slow and loud to keep up with the demand of a commercial soda dispenser.

So maybe if I can reduce the water pressure to 30psi, the water and CO2 will just mix as it flows in as needed.

 

[worxman02]

Ok according to kegman.net this is how motorized carbonation systems work:

A motorized carbonator consists of a carbonation tank into which flow carbon dioxide gas and pumped fresh water, both at pressures from 80 to 200 psi

So based on that, it seems like all i have to do is have a balanced pressure system and the water and gas will flow in as needed. Unfortunatly since it's friday all the plumbing and process engineers here at work are taking the day off, so I can't go confirm this with any of them. I'll have to wait till Monday. I won't have any time to work on it this weekend anyways.

 

[Tegra]

Wroxman:

I do almost the same!

Have a under-sink water filter that I have put a T on and a shut-off valve.

I then have about 50 feet of cheap pipe (humidifier, ice-maker) that I have coiled up under the sink. At the end is a liquid disconnect. (I used a liquid disconnect so I could also have a pressure gauge connected to watch the operation)

Then my water tank drops below about half, I disconnect both posts, uncoil the hose, purge about a cup out of the hose (by pushing the pin in with a spoon) to make sure there is "fresh" water, and connect it to the tank for at least 10 minutes.

The house pressure is about twice what I have the CO2 set for so it will stop filling when the empty space is half of what it started (If tank was 1/2 empty, this will fill it to 3/4) I do not have to worry about leaving it too long as the flow will stop when the pressure equalizes.

I like to do this at the end of the evening and then leave the keg disconnected overnight to give the now 55 PSI CO2 to get absorbed. By the next morning the pressure in the head space has dropped to the normal CO2 pressure and I connect the hoses and I am back in action.

I used to drag the keg out of the chest, fill and drag back and then wait the few days for CO2 to dissolve. I would waste quite a bit of CO2 opening an empty keg at 28 PSI and a lot of time waiting for the water to get cool and carbonate, not to mention the mess of the tank in the kitchen. My wife is content with a small hose across the kitchen for 10 minutes as long as I keep another keg full of champagne.

Since I am only topping up the keg, the temperature stays cool and the carbonation high. I was thinking of some way to "automate" this further but this method is "cheap and dirty", as long as I remember to do it every week or so.


Tom

 

[worxman02]

Wroxman:

I do almost the same!

Have a under-sink water filter that I have put a T on and a shut-off valve.

I then have about 50 feet of cheap pipe (humidifier, ice-maker) that I have coiled up under the sink. At the end is a liquid disconnect. (I used a liquid disconnect so I could also have a pressure gauge connected to watch the operation)

Then my water tank drops below about half, I disconnect both posts, uncoil the hose, purge about a cup out of the hose (by pushing the pin in with a spoon) to make sure there is "fresh" water, and connect it to the tank for at least 10 minutes.

The house pressure is about twice what I have the CO2 set for so it will stop filling when the empty space is half of what it started (If tank was 1/2 empty, this will fill it to 3/4) I do not have to worry about leaving it too long as the flow will stop when the pressure equalizes.

I like to do this at the end of the evening and then leave the keg disconnected overnight to give the now 55 PSI CO2 to get absorbed. By the next morning the pressure in the head space has dropped to the normal CO2 pressure and I connect the hoses and I am back in action.

I used to drag the keg out of the chest, fill and drag back and then wait the few days for CO2 to dissolve. I would waste quite a bit of CO2 opening an empty keg at 28 PSI and a lot of time waiting for the water to get cool and carbonate, not to mention the mess of the tank in the kitchen. My wife is content with a small hose across the kitchen for 10 minutes as long as I keep another keg full of champagne.

Since I am only topping up the keg, the temperature stays cool and the carbonation high. I was thinking of some way to "automate" this further but this method is "cheap and dirty", as long as I remember to do it every week or so.


Tom

Thanks for the detailed reply. I just talked to the only process engineer still working today and he basically told me something similar to your process. With a pressurized system, you are only going to be able to fill your keg up to half the amount of "empty" space since the gas law says that you can compress a gas by half or something like that. So you have to push the water in at twice the CO2 pressure with the gas off and then once the keg is filled, you turn the water off and turn the gas back on. The gas won't flow until the compressed CO2 gets dissolved and the pressure in the headspace lowers back down to below the set CO2 pressure.

Though I think based on what he told me, if you have a check valve in the gas line, all you need is a valve on the water line and when your keg gets half full, just open up the valve, let the water fill and pressurize the keg and then shut off the water again. Seems like you don't need to disconnect any lines if you have the water going in through the gas port. He also said you could use a float switch/valve to turn the water on and off when needed, but im not sure how to mount that in the keg and connect it to the water supply line. Sounds like more research and planning is in order.

 

[Tegra]

... He also said you could use a float switch/valve to turn the water on and off when needed, but im not sure how to mount that in the keg and connect it to the water supply line. Sounds like more research and planning is in order.

I was thinking of going completely crazy and having a weight switch or at least a water valve...... but I do not want to plumb water to the kegerator (on the porch) and buy a second water filter so the 10 minute bedtime ritual every couple of weeks is actually kind of fun.

The hose is actually long enough to reach the garage where the brew kettle is so I can stretch the kitchen water filter to everywhere I need it.

I doubted the $30 cost for hose/fittings/disconnect but I think it is serving me well.

Tom

 

[DrunkleJon]

I think the float switch would require compromising the keg somewhat unless you can somehow make it work through the prv hole. I think the best method would probably be to do the manual refills. maybe work with what you have already and add in a valve on the water so that you can just open it up every week? (if your gas has a check valve that is) until it stops filling, then turn off the water again and let the CO2 take over.

 

[worxman02]

I think the float switch would require compromising the keg somewhat unless you can somehow make it work through the prv hole. I think the best method would probably be to do the manual refills. maybe work with what you have already and add in a valve on the water so that you can just open it up every week? (if your gas has a check valve that is) until it stops filling, then turn off the water again and let the CO2 take over.

Yea, I think it will have to be a semi-manual system at this point unless I come up with a genius idea. I don't want to compromise the keg at all. Going through the PRV hole might work if I could fins something to match the threads. I guess having to open up a valve every couple of days isn't too bad. Wonder if I could use a programmable irrigation timer to fill the keg. Have it set to go on for 10 mins every third day or something. That way it's even more automated.

 

[crane]

Yea, I think it will have to be a semi-manual system at this point unless I come up with a genius idea. I don't want to compromise the keg at all. Going through the PRV hole might work if I could fins something to match the threads. I guess having to open up a valve every couple of days isn't too bad. Wonder if I could use a programmable irrigation timer to fill the keg. Have it set to go on for 10 mins every third day or something. That way it's even more automated.

I like this idea. I could use a solenoid valve and a spare arduino to add water every few days. The code would be really easy to write for that.

 

[Tegra]

It might not be too hard to sources pressure sensor that would turn on at about 24 pounds and off at 32. If It was slipped under the edge of a keg it could be connected directly to a solenoid valve. Although it would be nice to have this happen during "off hours" so the increased serving pressure does not frighten anyone.

I found I had issues with my back flow valves and I had to leave the gas disconnected until the pressure subsided overnight.

I figure this saves me about .50 cents every keg on CO2 because of leaving the pressure intact. (Probably twice that considering that hassle of getting a tank refilled)

My little concern is long term cleanliness? I am filtering out the chlorine in the tap water so there is essentially no sanitizer. Will the CO2 and cold temperature, plus the fresh water be enough to keep the whole thing safe?

Tom


Sent from my iPad using Home Brew

 

[AnOldUR]

I think the float switch would require compromising the keg somewhat unless you can somehow make it work through the prv hole.

I don't want to compromise the keg at all.

Personally, I have no problem putting a hole in the side of a keg. I already have a keg dedicated to seltzer and think that a mechanical solution is the way to go. This float vave is only 10 bucks from Amazon, is NSF approved and has a max rating of 100psi. Might take some mods to make it fit, but I think it's doable. Just ordered. Let you know how/if it works out.

 

[Tegra]

I'm still not so sure you want to fill (and over pressurize) as often as a simple float might. I am thinking to difference between the empty and full level would be about a foot. I think the float would turn on every few glasses of soda.


Sent from my iPad using Home Brew

 

[nfeuerhelm]

Personally, I have no problem putting a hole in the side of a keg. I already have a keg dedicated to seltzer and think that a mechanical solution is the way to go. This float vave is only 10 bucks from Amazon, is NSF approved and has a max rating of 100psi. Might take some mods to make it fit, but I think it's doable. Just ordered. Let you know how/if it works out.

I'm still not so sure you want to fill (and over pressurize) as often as a simple float might. I am thinking to difference between the empty and full level would be about a foot. I think the float would turn on every few glasses of soda.


Sent from my iPad using Home Brew

Assuming that you would only want to fill both when the level drops to the point where the float opens its valve and during "off hours" (say between 2am and 6am, though even 1hr per night would suffice). You could add a 120v solenoid and an automated switch. This way you would only add water when the level is low and the keg isn't in use. Then you would never have to worry about it unless you were to have a massive seltzer party and use the entire kegs worth in one night.

 

[ekjohns]

Here is what I would do. first make a spuding valve. This is an adjustable blow off valve see here for info on building one spuding valve

Gas side:
1. Co2 tank with regulator set to 30 psi going to a Y split (add a check valve to prevent anything getting to the regulator)
2. At the splitter one arm goes to the keg while the other goes to a spunding valve set to release pressure above 32 psi.

Liquid side:
1. Keg out to tap
2. Add a float valve to the lid of the keg with tap water in. I would just drill another hole with a ball lock liquid post to make it easy to open the lid and this would keep the prv intact in case the spuding valve fails. On the inside of the lid you can run some cheap rigid water line to the bottom of the keg for filling.

If I assume correctly when the water level drops too low the float valve opens and water comes in at ~45 psi. As the pressure gets above 32 psi (spuding valve set point) the pressure is released allowing for continued filling of water. Once the liquid gets high enough and shuts off the float valve then the keg is sitting at 32 psi. However, as the non-carbonated water mixes the pressure will drop and the co2 tank takes over to bring the pressure and carbonation back up. Also, every time you draw off the tap the pressure drop results in more CO2 being added to keep pressure constant. I think you will have to play around with the set points of the spuding valve to get it right above the regulator and the position of the float valve so as enough water is added to eventually drop the pressure low enough to add more co2 but not too low that there is any wait time for the new water to be carbonated.

 

[ekjohns]

If you took something like this and bent the arm at a 45 degree angle you could probably mount it to a lid and have it still function with a near full keg. Also saves you from killing a get by putting a hole in the side. Worse case scenario you are out a keg lid

 

[AnOldUR]

Had to try.