Guide to Water Feeders, Pressure Reducing Valves (automatic water feeder valves) on Hot Water (Hydronic) Heating Boilers
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Water feeder valves & pressure reducing valves on hydronic (hot water) heating boilers - how to install, adjust, maintain, repair
Automatic water feeder valves on boilers - adjust for building height
What is the normal operating pressure of a hot water heating boiler? Heating Boiler pressure guidelines.
What system pressure settings are needed for hot water heat
When and how to add water to a hot water boiler
Backflow preventers built into automatic water feeders on hot water heating system boilers
A look at the Amtrol Fill-Trol combination of expansion tank & automatic pressure-reducing valve / water feeder
Questions & answers about heating boiler pressure reducing valves, water feed valves, check valves: operation and repair

Here we explain hot water boiler pressure reducing valves and types of manual and automatic water feeder valves used on hot water heating boilers, including when and how to add makeup water to a boiler. A chart illustrates the adjustment to heating boiler operating pressure as a function of building height or the number of floors in a building being heated. We include photographs of common pressure reducer valves and water feeders used on hot water heating boilers to aid in product identification, links to installation manuals, safety warnings, installation and pressure reducer / water feeder safety and maintenance tips.

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Hydronic (hot water) Heating Boiler Water Feed Valves

If your heating system uses a steam boiler, see WATER FEEDER Valves, Steam. If you don't know what kind of heat your building uses, we explain how to figure out the answer at HEATING SYSTEM TYPES. If your heating system is not working properly, see NO HEAT - BOILER or NO HEAT - FURNACE. This article series answers nearly all questions about Heating System Boiler Controls on central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.

The photo above shows a modern automatic pressure-reducing water feeder valve on a hydronic (hot water) heating boiler - one of the safety controls which we discuss in this article. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Manual water feeder valves on hot water boilers

Hydronic (hot water boilers) in proper condition do not normally consume any water. Once the boiler and the baseboard, radiator, or convector piping are connected and filled with water, that same water remains in the system indefinitely. The water in the boiler is heated and circulated through the occupied space to provide heat to the building occupants.

Water may be lost from a hot water heating system, however, due to a small leak that may be un-noticed, or water may be removed from the system during servicing.

Some older heating systems may not have an automatic water feeder and may only provide a manually operated valve to add water to the boiler. To maintain the water level in these heating systems, water can be added from the building water supply piping manually by simply opening a make-up valve. A manual valve will simply be a shutoff valve that can be opened by hand to force water into the heating boiler.

Automatic water feeder valves on hot water boilers

On many heating boilers the expansion tank and water feeder valve are separate physical units.

On these older systems the "automatic water feeder" is often a bell-shaped device which opens and sends makeup water into the heating boiler and its piping whenever the heating system's internal water pressure falls below a normal level (perhaps 12 psi when the boiler is cold).

In our photo at left the gold colored bell-shaped device pointed to by the red arrow is an automatic pressure-reducing & water feed valve for a hot water boiler. An arrow cast into the valve base shows the direction of water flow (from building supply at right into the boiler at left in this photo).

The screw and lock nut on top of this valve permit adjustment of the automatic water feeder valve pressure (it's normally set to 12 psi).

The horizontal lever is a bypass that will send water through the valve on to the boiler at full building pressure (it's normally left "off" in the position shown here).

The separate heating system backflow preventer / check valve indicated by our green arrow is discussed in more detail at BACKFLOW PREVENTER VALVE, HEATING SYS.

Automatic Heating System Automatic Water Feeder Includes Built-In Backflow Preventer

The device to the right of the automatic pressure reducer (water feed valve) in our photo above is a back-flow preventer that is required in some municipalities. The back-flow preventer makes sure that water from inside the heating boiler cannot flow backwards into the building (and community) water supply. This prevents back-contamination of potable water piping from the boiler should the building water pressure fail. See CHECK VALVES, HEATING SYSTEM for more information about backflow preventers and other heating system check valves.

An automatic water feeder used on hot water heating boilers performs two functions:

Bell & Gossett's sketch of their pressure reducing valve is shown at left.

The automatic water feed valve reduces the incoming water pressure from the building supply side down to (typically) 12 psi. That's because the normal in-boiler water pressure, when the heating boiler is cold, is about 12 psi in a normal residential system. A tall building may need to start with higher cold-system water pressure to be able to push hot heating water to upper floors.
The water feed valve adds water to the boiler when needed: If water pressure in the heating boiler drops below 12 psi, the water feeder valve will add makeup water to the system automatically, until it reaches 12 psi inside the boiler.

So is the B&G Pressure Reducer an Automatic Water Feed Valve or Not?

Well yes, and no. The valve can automatically feed water into a hot water heating boiler whose pressure falls below the set-pressure (12 psi at factory setting) if the water shutoff valve for the boiler has been left "on".

BandG Pressure Reducing Valve (C) Bell & Gossett ITT The B&G pressure reducing valve shown at left includes a bypass lever shown in the "up" or "open" position in the illustration. In this position water is fed into the boiler at street pressure. When the valve is "down" in the "closed" position, IF the shutoff valve before the pressure reducer is open, water is fed to the boiler if its pressure drops below the valve's pressure setting (adjusted by the lock-nut and screw on the valve top).

But the manufacturer warns that the purpose of the pressure-reducing (and automagic water feeding) valve is to fill heating boilers after installation or servicing. The company says

"It is not a safety device and is not intended to be used as as a water feed valve to control boiler water at a safe operating level".

OPINION: this is interesting since for closed-system hydronic heating boilers (not steam boilers) that's how lots of service techs and inspectors view this device.

In the company's service manual you'll see on the installation piping sketch (edited) for the pressure reducing valve (green, to the right of the blue shutoff valve at the left side of the sketch below) that they expect the installer to include a water shutoff valve (blue at the left end of the sketch below) before this pressure reducer.

B&G wants you to keep the boiler water supply valve shut except during service - as a precaution that allows easy detection of a boiler leak by noticing the reduced water pressure in that system. In our experience most hydronic heating boiler installers and service techs leave that shutoff valve "open" or "on" so that the boiler won't be at risk of being ruined or unsafe by operating at low or no-water level.

A safety improvement on hydronic boilers that gets around this argument is to add a low-water cutoff on residential hydronic heating boilers (hot water heating boilers).

That device, always present on steam boilers, is required by local codes in some jurisdictions for hydronic heating boilers too. See Low Water Cutoff Valves, Boilers.

OPINION: on a hot water heating boiler that does not have a low-water cutoff valve installed, we would be reluctant to leave the building unattended for weeks or months during the heating season with the boiler water supply shutoff valve in the closed position.

We would think about leaving the water supply valve open - not what B&G recommends. That way if a small leak develops we're not at risk of destroying the boiler by firing it without adequate water in the system. This violates the B&G installation instructions for their pressure reducing valve - so be sure to review this concern with your trained, heating service company service manager.

Differences in Makeup Water Requirements - Hydronic Heat versus Steam Heating Boilers

In normal use, a hydronic or hot water heating system does not consume any water. Only if there is a leak (or during service) would the water level in a hot water heating system drop and need replenishment. That is an abnormal condition, and one that means the system needs to be repaired.

Keep in mind that devices like the B&G Pressure Reducer (notice they don't call it a "water feeder" even though it feeds water to the boiler) is intended for hot water or hydronic heating boilers.

But a hot water heating system might have a tiny, small, even hard-to-find water leak that goes un-noticed for some time, especially if the boiler water supply valve is kept open so that the pressure valve also feeds a little makeup water into the boiler when needed.

Conversely, on a steam heating system the boiler is expected to consume water at every operating cycle - the feed frequency is therefore much greater on a steam boiler and this B&G pressure reducer/water feeder would not be the proper device to use for water feeding. For water feeders used on steam boilers, see WATER FEEDER Valves, Steam.

The Pressure Reducing Valve (automatic water feeder) has two additional features:

Faulty pressure reducer valve (C) Daniel Friedman

Pressure Reducing Valve Override: Lifting the lever over the valve body (B&G valve shown at page top) will overcome the 12-psi feature and force water into the heating boiler at building pressure. This feature is not normally used, but it's useful during some service procedures such as refilling a boiler that has been drained (more rapidly than otherwise) or for temporarily forcing water into a heating boiler at high pressure for diagnostic reasons or to attempt to force air out of an air-bound hot water heating system.

Watch out: forcing cold water into a hot heating boiler can cause it to crack or be ruined. Keep this "shutoff valve" or override lever closed except during initial filling of the boiler or when manually adding fill to a cool or cold boiler as part of service.

Watch out: constant addition of fresh makeup water to a heating boiler that is leaking can make discovery of the leak more difficult, and by constantly introducing fresh water, can lead to mineral deposits, clogging, or boiler damage.

Watch out: take a look at the funny lever position on the pressure reducing valve in our photo (above-left). Is it closed, off-bypass (down) or is it partly open (up)? We weren't sure, but this very valve was blamed for a major house flood causing thousands of dollars in damage from mold. The building was unattended and the valve fed water into the structure for days, resulting in flooding and mold contamination. We wondered if the house-watcher made a mistake or was messing around with this device before the flood.
Pressure Reducing Valve Set-pressure Adjustment: The incoming water pressure setting of 12 psi can be adjusted up or down by the service technician.

The red Armstrong™ pressure reducing valve shown here includes a black plastic cap covering its adjustment screw under the black plastic cap on top of the valve.

You'll see a similar screw (and lock nut) on the B&G water feeder valve in the photos above on this page.

Loosening the lock nut and then turning the screw on the top of the pressure-reducing valve "in" or "clockwise" increases the set pressure of the control. See B&G's "Reducing Valves Installation, Operation, & Service Instructions" linked-to at References below.

Photo Guide to Heating Boiler Pressure Reducing Valves

Water feeder valve for a hot water boiler

Our photo at above left shows an Armstrong™ pressure reducing valve. The schematic at above right, courtesy of Carson Dunlop, explains how this pressure reducing valve works.

Pressure reducer water feed valve on Energy Kinetics boiler (C) Daniel Friedman

Our photo (left) shows another model of pressure reducer valve on the water supply line to an Energy Kinetics oil fired heating boiler.

The lever on the top of this valve combines a full-open bypass (when the lever is vertical) and a set-pressure adjusting locknut (below the round lever body).

Safety note: If the pressure reducing valve is combined with a pressure relief valve, for safety these parts must be installed in the correct position.

As Carson Dunlop shows in the sketch above, and as you'll also see in the B&G installation piping sketch, the pressure relief valve should always be installed closest to the heating boiler so that it can respond to an overpressure in the heating system.

What is the proper water pressure setting for a pressure-reducing valve or water feeder valve on a Hot Water Heating System?

What is the normal operating pressure of a hot water heating system boiler?

Hydronic heating systems (hot water) typically operate at about 12 psi cold and see a pressure increase to somewhere just under 30 psi when the system is at maximum temperature.

If you set the water feeder pressure too high it's likely that when the boiler heats-up to operating temperature, the water pressure will exceed the safety limit (30 psi) and the boiler relief valve will open to discharge excess pressure and water.

Because a hydronic heating system's circulator pump has little "lift" capacity (it just pushes the water around the loop of boiler and heating piping and radiators), the heating system depends on its internal water pressure to lift hot water to radiators (baseboards, or convectors) on upper floors in the building.

A higher building may therefore need higher heating system water pressure in order to be able to circulate heat adequately to upper floors. The sketch, courtesy of Carson Dunlop, explains that a three-story building will need heating system pressure set up to at least 15 psi. when the heating boiler is cold.

But in most cases you should leave the water feeder at the psi set by the installer (typical factory setting is 12 psi) unless the building has unusual conditions (such as more than two stories) that require a higher in-boiler starting water pressure.

Automatic Water Feeders Built-Into Expansion Tanks

An automatic water feeder valve is included as part of some heating system expansion tanks on hydronic heating boilers - in a single unit such as those provided by Amtrol™, Extrol™, Fill-Trol™, or similar expansion tanks.

The water feeder is the brass assembly found attached to the expansion tank where piping from the boiler enters the tank on these units.

In our photo at left you can see the brass valve on top of the Fill-Trol™ expansion tank and underneath the cast iron air purge valve (red arrow).

The vertical copper pipe is feeding water from the building supply, at building water pressure into the brass valve and through it, upwards into the heating system distribution piping through the silver painted cast iron air purge valve.

This automatic water fill valve is not adjustable by the consumer and is factory-set to add water to the heating boiler whenever the system pressure falls below 12 psi.

The tank below the red arrow is, of course, an expansion tank. We discuss expansion tanks and their troubleshooting or maintenance at Expansion Tanks.

Steam Boiler Water Feeder Valves, Automatic & Manual

Also see our detailed article on automatic water feeders for steam heating boilers, at WATER FEEDER Valves, Steam.

Keeping the proper amount of water in a steam boiler is a critical function for both safety and to avoid damaging the boiler itself. So on a steam boiler we consider the automatic water feeder to serve as a safety device too. Water feed valves on steam heat systems operate under very different requirements than those on hot water (hydronic) heating systems.

Automatic water feed valves on steam boilers (such as the McDonnell & Miller automatic water feeder shown at left) perform functions similar to the valve described earlier for hot water boilers.

Residential steam heating systems are mostly "low pressure" systems operating at less than 2 psi. In fact if you see the pressure set higher on a residential system it is often an indicator that the occupants/technician have been having trouble getting the steam heat to locations where it's needed. All steam heat systems all consume some water which escapes from radiator air vents during the time that the steam (heat) is first rising in the building. So unlike a hydronic water feeder, the steam boiler water feeder is going to be much busier, regularly adding makeup water to the steam boiler, but operating at low water pressures.

Steam heating systems without an automatic water feeder are less safe and risk serious boiler damage should boiler water be lost and should there be no low water cutoff installed on the system. That's why all modern steam heating boilers can be expected to include at least a low water cutoff valve. Low water cutoff valves are discussed in detail at Low Water Cutoff Valves, Boilers.

Frequently Asked Questions (FAQs) about heating boiler pressure reducing valves, water feed valves, check valves: operation and repair

Question:

I have a gravity feed system with water radiators in my home. When I leave the incoming water on the pressure in my system goes sky high the expansion tank discharges the water. When my system is full of water and I turn off the incoming water by the water feeder my system loses pressure and I have to add water again thru the water feeder. Is my water feeder the issue?? When the system loses pressure where is that water going?? The expansion tank is above my furnace in my basement. Any help would be appreciated!! Thanks, Fred

In regards to my gravity feed system "pressure" problem question -- Municipal water, system has been working fine for last 15 yrs. When system full of water home heats fine but when furnace off pressure drops. Thanks, Fred

Reply:

Fred,

Particularly with a gravity circulating system, that is you rely on hot water rising through the heating pipes by convection rather than by using a circulator pump, if there is not enough pressure in the heating system hot water may rise too slowly or even not at all to upper floors in the building.

Check the water pressure in your heating boiler (furnaces are hot air systems, water based heating systems are boilers) when the system is cold - for a typical 2 story home you'll want to see 12 psi cold pressure in the boiler.

If your boiler pressure is low and/or if you've had a leak and lost boiler water leading to low pressure AND if your water feeder valve is not working properly (or is not properly set) then you may have low boiler pressure.

Also take a look at "What is the proper water pressure setting for a pressure-reducing valve or water feeder valve on a Hot Water Heating System?" in the article above.

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WATER FEEDER Valves, Hydronic - See detailed links at page left

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (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.
B&G Flo-Control Valves - installation, operation, and service instructions manual - original source Bell & Gossett, 8200 N. Austin Ave., Morton Grove IL 60053, USA - Tel 847 966-3700 Fax 847 965-8379 . www.bellgossett.com/BG-Literature-Detail.asp?LiteratureID=607
B&G / ITT Reducing Valves, Instruction Manual V55999: Reducing Valves Installation, Operation, & Service Instructions, Bell & Gossett Air Separators and other heating system components, Bell & Gossett, 8200 N. Austin Ave., Morton Grove IL 60053, USA - Tel 847 966-3700 Fax 847 965-8379. Original source www.bellgossett.com/literature/files/610.pdf

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

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DUST CONTAMINATION FROM HVAC? An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
Fuel Oil & Oil Heating Magazine, 3621 Hill Rd., Parsippany, NJ 07054, 973-331-9545
Goodman Furnace High Temperature Plastic Vent HTPV safety recall US CPSC notice
Home Heating System Should Be Checked [for proper venting and for CO Carbon Monoxide Hazards - DJF]
Inspection Procedures for Oil-Fired Heating Systems Detailed step by step approaches for inspecting complex systems]
Lennox Pulse Furnace Safety Inspection/Warranty Program: Carbon Monoxide Warning
Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
Oil Tanks Above Ground, UL Standards, guidance for home owners, buyers, and inspectors
Plastic Heating Vent Pipe & Other Heating Safety Recall Notices
Weil McLain Model GV Gas Boiler/gas valve CPSC recall/repair
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
Links to our list of additional information on heating system inspection, repair, maintenance
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Hydronic (hot water) Heating Boiler Water Feed Valves

Manual water feeder valves on hot water boilers

Automatic water feeder valves on hot water boilers

Automatic Heating System Automatic Water Feeder Includes Built-In Backflow Preventer

An automatic water feeder used on hot water heating boilers performs two functions:

So is the B&G Pressure Reducer an Automatic Water Feed Valve or Not?

Differences in Makeup Water Requirements - Hydronic Heat versus Steam Heating Boilers

The Pressure Reducing Valve (automatic water feeder) has two additional features:

Photo Guide to Heating Boiler Pressure Reducing Valves

What is the proper water pressure setting for a pressure-reducing valve or water feeder valve on a Hot Water Heating System?

Automatic Water Feeders Built-Into Expansion Tanks

Steam Boiler Water Feeder Valves, Automatic & Manual

Frequently Asked Questions (FAQs) about heating boiler pressure reducing valves, water feed valves, check valves: operation and repair

Question:

Reply:

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair