Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER CONTAMINANT LEVELS
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PUMP REPAIR GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMP SHORT CYCLING
WATER SOFTENERS & CONDITIONERS
WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
This article describes snifter valves and Dill valves, what they are, how they regulate air in a well water system, and how they are installed, maintained, replaced, or eliminated. Snifter valves are a two-part air volume control system designed to maintain the air charge in a well water pressure tank on some submersible pump systems where a bladderless water tank is installed.
Snifter valves, used only on submersible well pump systems (the pump is inside the well), are a type of automatic air volume control system that adds a charge of air into the water pressure tank during each well pump on-cycle.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved.
Snifter Valves, Air Inflator Stems, & Drain-Back Vents for Air Volume Control in the Water Pressure Tank
Snifter valves provide an air inlet, typically located on a check valve on the water line near the bladderless water pressure tank. The air inlet work in concert with a water drain-back valve (a bleeder orifice) that you cannot see - located on well piping inside the well where a submersible pump is used.
In our snifter valve photo (left, Rasmussen Well Drilling, Inc., Two Harbors MN & DJ Friedman) ) my finger points to the stem of the air valve portion of the snifter valve; the valve is mounted on a bronze check valve. Stains on the floor show that there has been leakage at this valve.
At the end of a well pump on-cycle (when the well pump stops) the snifter air valve mounted on a check valve on the well line ahead of water pressure tank opens to allow air into the well piping. Water drains out of the well piping at a bleeder fitting mounted on a tee on the well piping, inside the well.
Later in this article we include photographs of the bleeder orifice drain back valve found on well piping where the snifter valve system is used.
The bronze check valve (on which the snifter valve is mounted in our photo) keeps water in the pressure tank from draining back down into the well when the well pump has stopped.
Because the snifter valve system will usually push more air into the water tank than is needed, an air release valve mounted on the water pressure tank is also installed to purge excess air from the water tank as necessary. So if you hear air hissing from the air purge valve, that's normal.
In our snifter valve photo (left) the green arrow points to the air release valve and the red arrow points to the snifter valve air inlet fitting mounted on a check valve.
Watch out: The snifter valve stem looks like any other air inlet valve but it uses a weak internal spring to allow the valve to open on its own, admitting air into the piping. DO NOT tighten the valve stem cap found on the snifter valve.
If you do so no air can enter the well piping and the system won't work. If you find water leaking out of the snifter valve it needs repair or replacement. You can temporarily tighten the valve stem cap to stop the water leak, but your water tank will lose its air charge, and until you've repaired or replaced the snifter valve, the water tank air will have to be added manually using other means that we describe at WATER TANK AIR, HOW TO ADD
In our photo above the snifter valve had not worked for years and was also leaky. You can see the copper stains on the floor below the valve (my finger points to the snifter valve stem).
The Snifter Valve System Drain-Back Fitting
These air volume control valve components are located inside the well on a tee on the well piping above the static head or about ten feet from ground surface in most installations. When the submersible well pump is "on" this drain back valve closes and water rises in the well pipe and into the building water supply system.
When the submersible well pump stops running, the snifter valve air inlet located at a check valve near the water pressure tank admits air into the well piping. In turn that entering air allows water in the well piping to drain back into the well through the small opening in the drain fitting located on piping in the well.
When the submersible pump starts running again, water pressure closes the drain back valve. Our photos below show how these valves function to open and close in response to water pressure in the piping.If the well pump is a submersible unit (located in the well) and if also the water pressure tank is a non-bladder type, there could also be one or even two air inlet valves installed on vertical section(s) of well piping inside the well.
Our photo at below left (Rasmussen Well Drilling, Inc., & DJ Friedman) shows the tee where the well service company worker has removed the air inlet vent detailed in our photographs found below.
The vent(s) are installed at a tee just above the top level of the static head of water in the well so that air can enter the vent during pumping cycles.
Water drains out and/or air is allowed into the well piping through the small orifice shown in the face of the air inlet valve shown at left. This is the valve we had removed from the well piping tee shown just above.
At the start of the next well pumping cycle, water pressure inside the pipe closes the vent valve and air inside the piping is forced into the pressure tank.
If the air inlet vent fails to close when the submersible pump is running, some water pressure, quantity, and flow delivery to the building will be lost.
Our well piping air volume control valve photographs below show the simple design of this well piping air inlet control valve. When the submersible well pump is off, pressure against the ball inside the air inlet valve is released, the ball can move away from the valve opening, and air can enter the valve. When the submersible well pump is on (pumping water), pressure against the ball inside the valve body closes the air inlet valve.
Snifter Valve Repair or Replacement
It's trivial to repair or replace the above-ground components of a snifter valve system as the parts are readily accessible. Be sure that you replace the internal snifter valve core with the proper parts. Using a valve stem core from an auto supply store may stop leaks at the valve but the spring will be too strong to allow the valve to admit air into the system when required - it will no longer work.
To replace the drain back orifice and valve shown immediately above it will be necessary to open the well and pull the well piping up sufficiently to reach and replace the device - a larger expense and more trouble as you can see in our photo (Rasmussen Well Drilling, Inc., & DJ Friedman).
A well service rig including crane and winch are needed to pull the well piping.
Why are Snifter Valve Air Volume Control Systems Used
There are a few reasons why a snifter valve air volume control system may be used along with a submersible well pump, bladderless-type water tank, and check valve.
Rasmussen points out that in Northern Minnesota and on water systems in other very cold climates, the system's ability to drain water back into the well, leaving just air in the higher sections of well piping can help protect a well system from freezing.
On water systems whose well provides water high in smelly hydrogen sulfide (that rotten egg smell) or perhaps high in iron, the high absorption of air into the well water provided by this design helps oxidize and thus reduce those contaminants in the water supply.
By contrast, a bladder type water pressure tank keeps the water supply physically separate from the pressure tank's air charge - air is never absorbed into the building water supply and other treatment methods would be needed to remove sulphur, hydrogen sulfide, or high iron levels.
Converting a Bladderless Water Tank to a Tank with an Internal Bladder? Remove all the Snifter Valve Components!
Watch out: if on a submersible well pump system that uses a snifter valve for air volume control you later convert a bladderless water pressure tank to a tank using an internal bladder, you should remember to remove both the snifter valve located on the check valve near the water pressure tank and the bleeder orifice or drain-back valve located on the well piping.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Use the search box below to ask a question or to search the InspectApedia.com website.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.