Bladder Type Water Storage & Pressure Tanks - Diagnosis & Repair InspectAPedia® -
How to diagnose and repair water system problems when an internal bladder water tank is installed
What is the difference between a bladder type water tank and a glass lined no-bladder water tank?
Broken, burst, busted or leaky water tank bladder
Well pump & water tank diagnosis & repair procedures
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This article describes the diagnosis and repair of internal bladder type water pressure tanks: how they work, what goes wrong, how to fix it.
Readers of this document should also see WATER TANK BLADDER PRESSURE ADJUSTMENT where we discuss adjusting air pressure in a bladder type water tank to factory specs, and also see Water pump and pressure tank repair diagnosis & cost an specific case which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost. The illustration at page top is courtesy of Carson Dunlop.
How Water Pressure Tanks Work - Pressure Tank Diagnosis
Private well and pump systems include a well (the water source), piping from the well to the building,
a water pump, and a water tank to which
building water supply plumbing is connected.
Building plumbing fixtures (sinks, toilets, showers, tubs) are
supplied with water from the building water supply piping, and drain into the building drain-waste-vent (DWV) system.
How water pressure tanks work
When water is turned on at a fixture in the building, compressed air in the water tank acts like a spring: it pushes water out of the water tank and into the building
water supply piping and thus water is sent on to the building plumbing fixtures.
If many fixtures are being run at once in the building, or if the water flow rate produced by the pump and piping and controls
is a modest one, the pump may run continuously all while the fixture is being operated.
More typically, if only one fixture is running and if the pump
and well can deliver a high water flow rate, the pump may come on and off several times while the fixture is being run.
As water leaves the water tank, water pressure in the water tank drops. Since the water tank also contains air, the air pressure drops too. In the tank water pressure and air pressure will be at the same psi. Sketch courtesy of Carson Dunlop.
A pressure control switch, usually mounted on or near the
water tank, senses the pressure drop, and at a pre-set "pump cut-in pressure" (typically 20 or 30 psi)
the pressure switch turns on the water pump. See WATER PUMP PRESSURE CONTROL ADJUSTMENT for details of this control.
The water pump, located at the tank or perhaps in the well, pumps water to the building from the well, simultaneously
re-pressurizing the water tank and providing water to the building. See WATER PUMP TYPES & LIFE EXPECTANCY for types of water well pumps, how they work, how they are diagnosed and repaired.
Because the water pressure tank is connected to the water pump (water in from the well) and also to the building water supply piping (water out to the building) the water tank is said to be "floated on the water line" and when the water pump is running water is pushed simultaneously into the water pressure tank and into the building supply piping.
The pressure control switch turns off the water pump when water pressure in the pressure tank
reaches the "pump cut-out pressure" (typically 40 or 50 psi) - pressure switch turns off the well pump.
What's the Difference Between a Bladder Type Captive Air Water Tank and a Conventional Steel Bladderless Water Tank
Bladder Type Captive Air Water Tanks
Bladder type or "captive air" water tanks (shown in our photo at left and in the sketch above) store the water tank's air charge in the upper portion of the steel water tank. Water in the tank moves in and out of a rubber bladder in the tank bottom. Because the air charge is kept separate from the water in the tank, air is not absorbed into the water and bladder type water tanks do not normally need to have makeup air added.
On some captive air water tanks this design is reversed. For example on the WellMate™ water tank the water is in the tank and air is in the tank bladder. This difference can confuse the burst water tank bladder diagnosis procedure which we describe below. At WATER TANK CAPTIVE AIR vs TRADITIONAL WellMate we provide separate water tank diagnosis and repair advice.
Water pressure or water pump short cycling problems with bladder-type water tanks are usually traced to a problem with the pump controls, with well and water piping leaks, or less often, to a failure of the internal tank bladder itself - a component that may be replaceable.
If the water-containing rubber bladder in a "captive air" water tank is defective (it can become stuck to itself and remain collapsed), the result can be a rapid on-off short cycling of the water pump. We test water pressure tanks to see if they're empty or nearly empty of water by seeing if we can gently rock or move the tank.
If the water tank is heavy with water it does not move easily. Be careful not to jiggle and break a pipe!
Water pressure tanks, their different types, how to identify them, and their repairs are described just above and in more detail at WATER TANK TYPES.
Traditional no-bladder Steel or Fiberglass Water Tanks
Bladderless Steel Water Pressure Tanks (photo at left and sketch just below) use a single steel tank interior to hold both the air charge and the water supply.
Modern steel bladderless type water tanks may be coated internally to increase the water tank life by resisting corrosion. That's what "glass lined" refers to on some water tanks. (A "glass lined" or "epoxy coated" water tank will not be a bladder type water tank which we discussed above.)
Bladderless water pressure tanks, because the air charge and water are in the same container, can lose their air charge over time (air is absorbed into the water) and may need air added. See WATER TANK AIR, HOW TO ADD for details.
Bladderless Fiberglass Water Pressure Tanks, such as the WellMate traditional hydro-pneumatic water tank operate similar to the steel water pressure tank, but incorporate a tank-top mounted air volume control and offer the advantage (over steel water tanks) of no risk of rust perforation and leak at the water tank.
Bladderless Fiberglass Water Pressure Tanks, such as the WellMate traditional hydro-pneumatic water tank operate similar to the steel water pressure tank, that is, no internal bladder is used to maintain and separate the tank's air charge and water charge pressure. These tanks incorporate a tank-top mounted air volume control and offer the advantage (over steel water tanks) of no risk of rust perforation and leak at the water tank. At WellMate Diagnosis we provide separate water tank diagnosis and repair advice for this water tank type.
What Goes Wrong with an Internal-Bladder type Water Tank?
Water pressure or water pump short cycling problems with bladder-type water tanks are usually traced to a problem with the pump controls, with well and water piping leaks, or less often, to a failure of the internal tank bladder itself - a component that may be replaceable.
Water tank bladder rupture: if the water containing bladder in a captive air water tank becomes ruptured, torn, or leaky, the result can be a very short water draw-down cycle before the water pump runs,or rapid on-off short cycling of the water pump. Water from the tank bladder leaks out of the bladder and into the steel tank itself where it replaces more and more of the air charge until finally the behavior of the water system is much as in the water tank bladder collapse discussed just below.
A water tank bladder might rupture from age, an internal defect, or if the pump pressure control switch is defective or is set so high that the water pressure breaks the bladder but this last cause is a bit unusual since the air pressure and water pressure on the two sides of the tank bladder's are normally the same.
Water tank bladder collapse: if the water-containing rubber bladder in a "captive air" water tank is defective (it can become stuck to itself and remain collapsed), the result can be a rapid on-off short cycling of the water pump.
We check water pressure tanks to see if they're empty or nearly empty of water by seeing if we can gently rock or move the tank. If the tank is heavy with water it does not move easily. If the water pressure tank is empty or nearly so, it will be very light and easy to move. Be careful not to jiggle and break a pipe!
Why don't we just look at the water tank pressure gauge to see if there is water in the tank? Well we do. But because debris or other failures can cause a water tank pressure gauge to read pressure even when there is none in the tank (the gauge can get "stuck"), we don't rely on just tank gauge readings. For more about water tank pressure gauges, see WATER PRESSURE GAUGE ACCURACY and see WATER TANK BLADDER PRESSURE ADJUSTMENT.
If the water tank is empty or nearly so, then water is not entering the tank. If the water pump runs but no water is entering the tank, the problem could be a collapsed bladder that is stuck onto itself, not admitting water. There could also be another problem such as a defective water pump, a well line leak, or other cause for water not entering the tank - so you may need to also see WATER PRESSURE LOSS DIAGNOSIS GUIDE.
If the water tank is "full" or nearly so, then if there is still no water pressure, the tank bladder could be also burst but the tank may have lost its air charge (over time air is absorbed into the water - the burst-bladder water tank is acting like a bladderless water tank discussed just above). In this case you might observe that the well pump (or pump control) is switching rapidly on and off when water is run in the building - see WATER PUMP SHORT CYCLING.
Bladder type or captive-air water pressure tanks and their repairs are described just above and in more detail at WATER TANK TYPES.
Diagnosis of a burst water tank bladder: if you remove the cap from the air valve on the top of your water tank and depress the pin in the center of the valve, normally air will hiss out. Don't hold this valve pin down or you'll lose the air charge. But if water comes squirting out of this air valve, the captive-air bladder type water tank has burst or become torn or leaky, and repair is needed.
A second symptom of burst water tank bladder: if air is found squirting out of plumbing fixtures it's possible that the cause is a burst bladder in the water tank; the tank's air charge is being forced out into the building plumbing system.
A third symptom of burst water tank bladder: if the water tank is full or nearly so and you are unable to drain water out of the tank, a burst bladder may be blocking the tank at its bottom. A burst water tank bladder can collapse at the water tank bottom, preventing water from leaving the tank. The result is no water pressure in the building and perhaps an inability to drain water from the water tank itself.
At WellMate Diagnosis we provide separate water tank diagnosis and repair advice for captive-air water tanks in which the air is in the bladder and the water is outside the bladder in the water tank.
Thanks to Jeff Garmel for suggesting text clarification in this discussion of water pressure tank diagnosis.
Water Tank Not Properly Located: if you place the water pressure tank too far from the pump pressure switch, or at a different elevation from the pressure switch, the pressure switch control may not operate properly. Here is what Amtrol™ says about tank location:
The Well-X-Trol should be installed as close as possible to the pressure switch. This will reduce the adverse effects of added
friction loss and pressure switch bouncing, and the difference in elevation between WELL-X-TROL and switch.
Really most pressure tanks will work if placed almost anywhere. But if you have a problem such as pressure switch bouncing (the switch turning the pump on and off rapidly at the start or end of a pumping cycle) you can relocate the pressure switch to the new larger tank and run a longer wire to the pump or pump control relay. Other causes of pressure switch bounce and well pump short cycling are explained at SHORT CYCLING CAUSES.
How do We Repair a Water Tank with a Burst Internal Bladder?
Repair of a leaky or burst water tank bladder: some people recommend treating the water tank as if it were an older bladderless type of water pressure tank such as the tanks we discuss at STEEL WATER TANKS.
It is unlikely that this will be a satisfactory repair. Usually when a captive air water tank bladder ruptures and water enters the rest of the steel tank, the bladder collapses; it often becomes impossible for the water pump to push much water into the water tank, and even if it does, the collapsing bladder will stick to and seal itself so that the water draw-down quantity before the pump needs to run again will be very small.
Fixing or getting rid of a waterlogged collapsed-bladder water tank: as we mentioned above, it's also possible that the torn bladder will stick to the water outlet opening, blocking water from leaving the water tank. The result will be short cycling of the water pump. We discuss water pump short cycling at WATER TANK REPAIRS. In any case the drawdown volume will be reduced and it's likely that this misused water tank will rust through soon.
Reader Bill Kortebein described how he identified and repaired this problem.
My pump was short cycling like crazy. So I drained the tank, measured the air pressure; it was zero, so I pumped it up to a couple PSI below the cut-in point.Short cycling improved a little…
But in a matter of a couple weeks or so, short cycling was just as terrible again. So I drained the tank again (this time the pipes were disconnected at the bottom of the tank – so I ought to be able to get all the water out, right?). I measured the air pressure: it was back to zero again. Pumped the tank back up again (which forced some more water out). Then tried rocking the tank, and the thing was still practically full, it was almost immovable.
No water ever squirted out the air pressure valve, but…
With the pipes open to the air at the bottom of the tank,
and the pressure pumped up (38 PSI)
I was only able to get a small percentage of the water out of the tank.
The only conclusion I could come to was that the bladder was burst, and that it was lying in a bunch at the bottom and somehow plugging the outlet. Does that conclusion make sense to you?
In any case, I replaced the pressure tank (and also installed a cycle-stop valve), and now the pump hardly ever turns on at all, compared to the way it was before.
Since the old tank was practically immovable, someone suggested I drill a hole in the side to let the water out. Pretty good idea, except not with the pressure pumped up to 38 PSI. Once I punctured through, it shot out like to drill a hole in me or anything else in its way, geysered all over the electrical stuff (and tripped the GFCI -- good thing there was one there), and kept me occupied containing this water knife for a good 15 minutes or more).
You need to replace the water tank bladder or as most plumbers recommend, replace the entire water tank assembly. If you are going to drill a hole to drain a blocked water pressure tank, we suggest disconnecting the tank entirely from its fittings and using a hand truck to get the heavy tank outdoors before drilling into it.
Water tank bladder replacement: on some water pressure tanks, the water tank can be disassembled and the bladder replaced. You might want to ask your plumber to try this repair before replacing the entire water tank assembly. Bladder replacement will involve draining water from the system and removing the water tank pretty much as if the whole tank were to be replaced. Suppliers such as Wessels offer replacement bladders for some models of expansion tanks and hydropneumatic tanks. In general, if you're going to hire a plumber to do this job, we recommend replacing the whole tank.
Water tank bladder air pressure adjustment: Be sure to review WATER TANK BLADDER PRESSURE ADJUSTMENT if you are adjusting, tuning, or replacing the air pressure in your bladder-type well tank.
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If Your Water Tank is Not Working Properly See These Diagnostic Guides
Thanks to Jeremy Houser who suggested that we needed to clarify the difference between bladder type and non-bladder type water tanks when discussing air charging and diagnosis of water tank repairs.
Amtrol Extrol™ pressure control tanks used on hydronic heating and other systems such as models 35LBC, 50 LBC, 85 LBC, and 100LBC to 600 LBC also use a bottom bladder containing air - see amtrol.com/pdf/LBCSeriesEXTROL9017-095.pdf for details.
Carson Dunlop, Associates, 120 Carlton Street Suite 407, Toronto ON M5A 4K2Toronto. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Thanks to Jeff Garmel for discussing clarifications on water pressure tank testing and diagnosis, 8/24/2009.
Thanks to Bill Kortebein for discussing dealing with a water-logged collapsed bladder water pressure tank 11/24/2009
Wessels Company bladder replacement store was found at westank.com/bladder-tank-store.php on 5/22/2009. Wes sell refers to "shock and surge tanks" as ASME replaceable bladder type and pre-charged hydropneumatic tanks used for commercial, industrial, and well water systems.
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