Dead Men Tales: Why Compression Tanks Waterlog

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Why Compression Tanks Waterlog

In this episode, Dan Holohan shares the history of expansion and compression tanks, along with some troubleshooting tips.

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Thank you to SupplyHouse.com for supporting this podcast.

Jamie Hall

Then someone comes along and adds an air eliminator to a system with a compression tank, Airtrol or no, and guess what? The tank waterlogs... but if one understands them, they will last forever.

There is an interesting variant on them which was used in the bad old days on wells with submersible or turbine pumps. Nowadays, of course, there is a check valve on such critters down at the outlet from the pump. More on that in a moment. But in the old days, there wasn't, and when the pump shut off the riser pipe drained. When the pump turned back on, the air in the riser pipe was supposed to go into the compression tank. We called them hydropneumatic tanks. That was always more air than was needed to replenish the air cushion in the tank -- so there was a float valve in the tank, which was supposed to release enough air to bring the tank water level up to where it belonged (perhaps I should point out that some really big ones had an air compressor to help things out -- but those were really big, like thousands of gallons). All this usually worked pretty well. If the float valve failed, though, the tank could spew water from it (annoying) or the tank could becomee airbound, equally annoying. But easily fixed. Bubbles are fine in champagne, but not appreciated in normal conditions. What happened, though, is eventually someone replaced the pump -- and the new pump had the check valve. Now you didn't get a charge of air when the pump started, and the tank waterlogged remarkably quickly and the water pressure went squirrely -- not to mention the pump started and stopped much too often and failed. The solution to that was to install diaphragm tanks instead. Of course, no good deed goes unpunished, so if you had diaphragm or bladder tanks, and that nice check valve failed, you got air in the tank on the water side, and they airbound...

hot_rod

Jamie Hall said:

Then someone comes along and adds an air eliminator to a system with a compression tank, Airtrol or no, and guess what? The tank waterlogs... but if one understands them, they will last forever.

There is an interesting variant on them which was used in the bad old days on wells with submersible or turbine pumps. Nowadays, of course, there is a check valve on such critters down at the outlet from the pump. More on that in a moment. But in the old days, there wasn't, and when the pump shut off the riser pipe drained. When the pump turned back on, the air in the riser pipe was supposed to go into the compression tank. We called them hydropneumatic tanks. That was always more air than was needed to replenish the air cushion in the tank -- so there was a float valve in the tank, which was supposed to release enough air to bring the tank water level up to where it belonged (perhaps I should point out that some really big ones had an air compressor to help things out -- but those were really big, like thousands of gallons). All this usually worked pretty well. If the float valve failed, though, the tank could spew water from it (annoying) or the tank could becomee airbound, equally annoying. But easily fixed. Bubbles are fine in champagne, but not appreciated in normal conditions. What happened, though, is eventually someone replaced the pump -- and the new pump had the check valve. Now you didn't get a charge of air when the pump started, and the tank waterlogged remarkably quickly and the water pressure went squirrely -- not to mention the pump started and stopped much too often and failed. The solution to that was to install diaphragm tanks instead. Of course, no good deed goes unpunished, so if you had diaphragm or bladder tanks, and that nice check valve failed, you got air in the tank on the water side, and they airbound...

I had a call on one of those air floats in a galvanized tank just last week. Plenty of them still around and you can buy those galvanized tanks and air level floats still. Wessels and others build plain tanks for well or boiler compression use.

leonz

I am certainly glad I have a B+G/Wessels 15 gallon steel compression tank on my heating system.

leonz

Jamie Hall said:

Then someone comes along and adds an air eliminator to a system with a compression tank, Airtrol or no, and guess what? The tank waterlogs... but if one understands them, they will last forever.

There is an interesting variant on them which was used in the bad old days on wells with submersible or turbine pumps. Nowadays, of course, there is a check valve on such critters down at the outlet from the pump. More on that in a moment. But in the old days, there wasn't, and when the pump shut off the riser pipe drained. When the pump turned back on, the air in the riser pipe was supposed to go into the compression tank. We called them hydropneumatic tanks. That was always more air than was needed to replenish the air cushion in the tank -- so there was a float valve in the tank, which was supposed to release enough air to bring the tank water level up to where it belonged (perhaps I should point out that some really big ones had an air compressor to help things out -- but those were really big, like thousands of gallons). All this usually worked pretty well. If the float valve failed, though, the tank could spew water from it (annoying) or the tank could become air bound, equally annoying. But easily fixed. Bubbles are fine in champagne, but not appreciated in normal conditions. What happened, though, is eventually someone replaced the pump -- and the new pump had the check valve. Now you didn't get a charge of air when the pump started, and the tank waterlogged remarkably quickly and the water pressure went squirrely -- not to mention the pump started and stopped much too often and failed. The solution to that was to install diaphragm tanks instead. Of course, no good deed goes unpunished, so if you had diaphragm or bladder tanks, and that nice check valve failed, you got air in the tank on the water side, and they airbound...

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YUP, lived through that again this year, I hate diaphragm tanks for well water; having had three of them replaced over 4 decades as they are a waste of money.

My inlaws had a vertical steel water tank with a float control and air charge that came with the house in 1946 and it lasted for 40 plus years for a family of 6 before it had a pin hole leak.

JUGHNE

There is a 1961 school that has the original compression tank.
I have serviced this place since at least 2006.

The tank would get water logged. Figured out the air vent on the supply was robbing all the air from the tank......removed that and got improvement.

Then realized the top sight glass stop valve was leaking some air.
Repacking and cleaning, replacing top sight glass gasket etc eliminated the problem completely.
It has been many years since the tank waterlogged. It sits at half full.

It has all the components for air collection out of the boiler air scoop, the airtrol inlet device,
3/4" piping with the slope as advised.

The pump is on the return to the boiler, as it was in those days.

leonz

JUGHNE said:

There is a 1961 school that has the original compression tank.
I have serviced this place since at least 2006.

The tank would get water logged. Figured out the air vent on the supply was robbing all the air from the tank......removed that and got improvement.

Then realized the top sight glass stop valve was leaking some air.
Repacking and cleaning, replacing top sight glass gasket etc eliminated the problem completely.
It has been many years since the tank waterlogged. It sits at half full.

It has all the components for air collection out of the boiler air scoop, the airtrol inlet device,
3/4" piping with the slope as advised.

The pump is on the return to the boiler, as it was in those days.

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I just love the simplicity of a steel compression tank, Internal Air Separator and airtrol valve.

If I knew then what I know now 40 years later, I would have never let the plumbers that put in my hand fed wood and coal boiler remove the saddle tank open to air steel expansion tank and it would still be in the ceiling of the laundry room.

Gilmorrie

My 70-year-old hot-water boiler still uses its origninal compression tank. It never requires maintenace. It has two B&G airtrol fittings - a tank fitting and a boiler fitting. My understanding is the tank fitting makes it easier to fill the tank when empty - which I seldom need to use. The boiler airtrol fitting's purposes is to separate air from the hot-water supply and return it to the compression tank. My understanding is different from Dan's.

Yes, my circulator is on the boiler return, and the compression tank is on the supply.

mattmia2

So the airtrol fitting doesn't control air, it just gives the water some resistance to flow so you don't get gravity circulation.

DanHolohan

Exactly.