Automatic water feeder on steam boiler (C) Daniel FriedmanWater Feeder Valves on Steam Heating Boilers

  • WATER FEEDER VALVE, STEAM - CONTENTS: how the automatic water feed valve works on a steam boiler; how often to manually add water to a steam boiler, What system pressure settings are needed for hot water heat.
  • POST a QUESTION or READ FAQs about how and when to use and maintain the water feed valve on steam boilers; diagnosis of causes of steam boiler over-filling or water feed valves that don't shut off.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Water feeder valves on steam heating boilers:

Automatic & manual water feeders. Here we explain the various types of manual and automatic water feeder valves used on steam heating boilers, including when and how to add makeup water to a boiler.

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.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Steam Boiler Water Feeder Valves, Automatic & Manual

Steam boiler sight glassThe photo at page top 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.

[Click to enlarge any image]

Our photo at left shows the steam boiler sight glass - a key place to look when checking that the steam boiler water level is set properly. More information about using the sight glass to maintain steam boiler water levels is included in the article below.

Article Contents

Water feed valves on steam heat systems operate under very different requirements than those on hot water (hydronic) heating systems.

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.

But 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.

Automatic water feeder valves on steam boilers

Steam boiler water feeder Steam boiler water feeder

Automatic water feed valves on steam boilers such as the McDonnell & Miller™ automatic water feeder shown at above left and the Hydrolevel Co. VXT 120 programmable water feeder at above right perform functions similar to the water feed valve described
at WATER FEEDER VALVE, HYDRONIC BOILER and used on hydronic (not steam) heating boilers.

But while a hydronic boiler does not normally consume water, a steam boiler always consumes water during normal operation. This means that some method for checking and keeping water in the boiler is critical both for safety and to assure against loss of heat.

A steam boiler will be damaged or unsafe if its water level falls too low. The water feed valve on a steam boiler has to operate more often, and will be a more heavy-duty (and probably reliable) device than that used on hot water heating system boilers.

What's the Difference Between the Two Water Feeders Shown Above?

Each of the devices shown in the two photos above is a water feed valve. On a signal (normally from the low water cutoff valve) the water feed valve will open to send additional makeup water into the steam boiler.

The McDonnell & Miller float operated water feed valve will automatically send water into the steam boiler if water falls sufficiently to activate its float. The piping and position of the valve determine how it maintains water level in the boiler. The yellow-handled manual ball-type valve in our photo at above left is a water feed bypass for manual water feeding - a step that we discuss just below.

The VXT Programmable Water Feeder from Hydrolvel is a universal control that can be used with just about any float-type low water cutoff. Models are sold that operate on both 24-Volt and 120-Volt power. The digital display we see in the unit above is a count of the amount of water that has been added to the boiler.

That information can be helpful in diagnosing boiler leaks or excessive water usage - two conditions that are especially important in the life of a steam boiler, but that are concerns on any water-based heating system. The following information is adapted from the Hydrolevel Company's product literature cited at REFERENCES.

Really? while we have not found reliable research nor an authoritative citation, we have read some heating website authors' posts describing buzzing and product failures in the Hydrolevel VXT unit. Other installers acclaimed the unit. [9]

Also see CHECK VALVES, HEATING SYSTEM where we discuss backflow preventers that may be required on some steam heating system water feeders.

Manual water feeder valves on steam boilers

Water feed valve override button (C) D FriedmanIn our photo at left, a close up of our page-top photo, you can see a "manual water feed" button on the top of the automatic water feed valve.

This button permits overriding the automatic feature of the valve to force water into the steam boiler.

But on lots of steam boilers, especially older residential units, you may find that only a manual feeder valve is installed. You'll need to use it to manually add water to the steam boiler whenever its water level is low. Below we discuss the detailed procedure for manually adding water to a steam boiler.

In our photo above at automatic water feed valves, an automatic water feeder is installed. But the yellow valve handle is an manual water feeder that will bypass the automatic water feeder and force water into the boiler. On this particular system you shouldn't need to use the manual feeder lever unless the automatic feed valve is broken.

As you'll see in that photo, the yellow handle is in the horizontal position, "across" the water pipe, showing that it is in the "closed" position (we're depending on the automatic feed valve).

How often you'll need to manually add water to a steam boiler that lacks an automatic feeder depends on how rapidly your particular steam heating system loses water. If you are new to your particular steam heat system, you should check it's water level (and flush the low water cutoff valve) at least weekly until you know more accurately how the heating system behaves in normal use.

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 & blowdown valves, an important safety device that shuts down the boiler if water level falls to an unsafe position, are discussed in detail along with step by step instructions in using the blowdown valve

When, How, & How Much Water to Add to a Steam Boiler

Steam boiler sight glass

If your steam boiler has an automatic water feeder you should see the water level always close to the fill-mark and the automatic water makeup valve will normally do this job for you.

When to add water to the steam boiler

If your steam boiler has only a manual valve for adding water, until you know the system's rate of water usage, you should check the water level at least once a week during the heating season.

You'll want to add water whenever the sight glass shows that the water level has dropped to the "add" mark and you should always see some water in the sight glass.

How much water to add to the steam boiler

The sight glass on a steam boiler, combined with a mark or gauge usually placed on the sight glass or on the boiler body behind the glass, will show the proper level to which the steam boiler should be re-filled when it's low on water.

Details are
at SIGHT GLASS, STEAM BOILER - a key component that shows when boiler make-up water is needed and how much to add manually.

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. This website answers nearly all questions about central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.

Steam Boiler Water Feeders References & Manuals


Continue reading at STEAM BOILER SIGHT GLASS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Or see STEAM BOILER FLOODING REPAIR where we explain the causes of water too high in the sight glass or in the steam boiler.



Or see WATER FEEDER VALVE, STEAM FAQs for more diagnosis and repair help with water feed valves on steam boilers

Or see WATER FEEDER VALVE, VXT-24 FAQs if your water feeder is a Hydrolevel VXT-24 programmable water feed valve

Suggested citation for this web page

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


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Questions & answers or comments about how and when to use and maintain the water feed valve on steam boilers

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman