Watch out: this is not only an improper heating system operating setup, it is potentially (though subtly) quite dangerous:

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.

This dual check backflow preventer with intermediate atmospheric vent is designed to protect drinking water systems from the return, caused by backsiphonage or backpressure, of contaminated fluids.

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.

Here we explain hot water boiler (hydronic heat) 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.

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.

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

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.

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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.

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.

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

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.

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I purchased this glycol pump as part of the build your own, which included the manifolds pump, expansion tank, air separator and basic plumbing supplies. I was very happy with how everything arrived together and the install was straightforward just from looking at the pictures. The glycol pump makes it easy to charge the system, and took a lot of the guesswork out of setting it up. My garage now has toasty warm floors.

If the valve were in manual OPEN mode, the lever would be at right angles to the piping and valve body - its handle would be over the adjustment screw shown in the center of the valve top. So this valve is in the CLOSED position.

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.

This article series answers nearly all questions about Heating System Boiler Controls on central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.

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.

A higher building may therefore need higher heating system water pressure in order to be able to circulate heat adequately to upper floors.

(The heating boiler, not shown here, is always on the outlet side of the valve, and on most of these controls an arrow cast into the valve body indicates the intended direction of water flow.

The valve valve, this one is a B&G model, has the job of feeding makeup water to the heating boiler should the water pressure in the heating system fall below the set-pressure on the valve - typically 12 psi for most one or two story residential buildings, though the set pressure may need to be higher in taller structures.

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.

Continue reading at PRESSURE REDUCING VALVE WATER FEEDER INSTALLATION or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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.

B&G offers some excellent tips on how to check the pressure reducer for proper operation, and how to fix some common problems.

What should Pressure on Pressure reducing valve on boiler be? Should I have this pressure reducing valve be set to a specific value?

An automatic control valve regulates a flow or a pressure of a fluid without external power source, no actuator is necessary resulting both in a most reliable ...

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Perhaps the heating service technician was annoyed by an owner's emergency service call complaining that the pressure / temperature relief valve was spilling and perhaps the tech found that the owner had been messing with the valve and over-pressurizing the boiler. If you set the boiler water pressure too high when cold then when the boiler heats up the pressure will exceed the (roughly 30 psi) pressure at which the relief valve will open.

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.

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.

Home inspectors are expected to be competent to recognize conditions at a home that are improper, unsafe, not functional, etc. provided that the problem or component is readily accessible, visible, and under some other conditions.

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).

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.

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

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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.

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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.

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.

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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).

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.

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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).

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In my [DF] opinion, a typical building owner or occupant almost never thinks to check the water level in a hydronic heating system (hot water boiler) until there is some indication of a problem (like no heat or a damaged leaky boiler).

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.

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This dual check backflow preventer with intermediate atmospheric vent is designed to protect drinking water systems from the return, caused by backsiphonage or backpressure, of contaminated fluids.

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).

Hydronic heating installations are invisible (with no vents or ducts on floors or walls) and silent in rooms as radiant heat rises from the floor surfaces of ...

The sketch, courtesy of Carson Dunlop Associates, explains that a three-story building will need heating system pressure set up to at least 15 psi. when the heating boiler is cold.

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Watch out: The manufacturers of this type of automagic water feed valve recommend that additional manual control valves be included in the piping system, so in some installations you might also find that the automatic water feeder is not really so automatic.

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

An earthquake-actuated automatic gas shutoff valve is attached to the natural gas pipeline between the meter and the house, downstream of the meter, to stop the ...

Tom Sherman - President, Absolute Home Inspection, Inc., 315-673-1755 provided this photo of a tied-off pressure-reducer water-feed valve and asked what we'd say about it, for an ASHI home inspector newsletter.

The override lever is used to put the water feed valve into "bypass mode" by lifting the lever to a 90-degree position above the water piping and valve body - meaning that the valve is manually forced "open" to allow water to enter the heating boiler at whatever pressure is on the inlet side of the valve.

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.

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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.

WATER FEEDER VALVE, HYDRONIC BOILER at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

In our photo we've drawn a blue arrow showing the direction of water flow for this valve. Click the image to see an enlarged version.

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.

... 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

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 company also points out that too-frequent feeding of water into a heating system can increase the effects of corrosion and system damage.

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.

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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.

This is the second unit I’ve installed as the first one, installed two winters ago in another building is working so well. No problems, easy to install. Both systems are hydronic floor heat and these units work great. Just fyi…….going to electric now works out cheaper than the original propane costs. Like that it’s Canadian made.

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.

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.

"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".

The separate heating system backflow preventer / check valve indicated by our green arrow in the photo above is discussed in more detail

"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".

The manufacturer is telling you what's safe in some regards, but they may not have the same view of what people actually do in the field.

I bought these to replace some wax actuators from my old system. Those were inconsistent (each moved a different amount) and had huge in rush power requirements. These have low power requirements and appear to be very consistent.

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 dual check backflow preventer with intermediate atmospheric vent is designed to protect drinking water systems from the return, caused by backsiphonage or backpressure, of contaminated fluids.

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).

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).

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".

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).

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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.

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.

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.

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.

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.

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

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 - their experience may be similar to mine.

But a more likely reason this valve was tied OFF or CLOSED was that it was leaking, feeding excess water pressure to the boiler on its own. One of the failure modes of these valves is that the valve begins to feed water when it should not. That can happen due to dirt and debris in the valve or for other reasons. Someone was trying to force the valve to behave itself.