High vs Low Pressure Steam: How to Label Valves Correctly (HPS vs LPS)
Steam systems are not all the same. Some buildings have high pressure steam coming from the boiler plant, and some have low pressure steam after a pressure reducing valve (PRV). The problem is… the valves can look almost identical.
If your valves aren’t labeled clearly, techs can shut off the wrong steam line, waste time during troubleshooting, or create a safety risk.
That’s where HPS and LPS valve tags come in.
What HPS and LPS mean (simple explanation)
HPS = High Pressure Steam
This is steam that is still at the higher pressure coming from the boiler or plant side. You’ll usually see it:
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On the main steam header
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Feeding PRV stations
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Feeding major steam equipment before pressure is reduced
LPS = Low Pressure Steam
This is steam after the pressure has been reduced, usually by a PRV station. You’ll usually see it:
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Leaving the PRV station outlet
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Feeding steam coils
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Feeding humidifiers
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Feeding heat exchangers
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Serving branch systems throughout the building
Bottom line: HPS is usually “before the PRV.” LPS is usually “after the PRV.”
Why separating HPS vs LPS matters
1) Safety and risk control
Higher pressure steam can be more dangerous. Clear labels help techs know what system they’re working on.
2) Faster troubleshooting
When a coil isn’t heating, the first question is often:
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“Do we have steam on the low pressure side?”
If your tags say LPS, it’s faster to trace the path and find the right isolation valve.
3) Better communication
Instead of saying:
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“Close that valve near the PRV”
You can say: -
“Close HPS 007 (inlet) and LPS 012 (outlet).”
That saves time and reduces mistakes.
Where to tag valves in a PRV station (best practice)
A PRV station is one of the most important places to label correctly.
Here’s a simple, clean method:
HPS Tags (High Pressure Side)
Tag valves on:
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PRV inlet isolation
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Strainer isolation (if present)
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Bypass line valves (if the bypass is high pressure)
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Any branch valves that are clearly still on the high pressure side
LPS Tags (Low Pressure Side)
Tag valves on:
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PRV outlet isolation
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Low pressure distribution header valves
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Coil/humidifier branch isolation valves (if they’re on the low pressure system)
Bonus tip: label bypasses clearly
Bypass valves confuse people. If you have a PRV bypass, tag it clearly and note it on your valve list. Many problems come from bypasses being open when they shouldn’t be.
A simple labeling format that works
Most teams use:
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HPS 001, HPS 002, HPS 003…
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LPS 001, LPS 002, LPS 003…
Or if you want one shared sequence:
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HPS 101–199
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LPS 201–299
The goal is simple: a tech should know the pressure system just by reading the tag.
Where to place HPS and LPS valve tags
Put the tag where it’s easy to see when you walk up to the valve:
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On the valve handwheel stem (chain/loop)
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On the valve yoke or body near the operator
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On a nearby support if the valve is insulated
Avoid tags that:
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get buried under insulation
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rub constantly on hot pipe
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hang into moving parts
Keep a “Steam Tag Master List” (this is the secret weapon)
A good tag system isn’t just tags. It’s also a simple list that connects the tag to the real world.
Your list can be a spreadsheet with:
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Tag number (HPS 004)
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Location (Boiler Room PRV Station #2)
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What it serves (PRV inlet to East Wing)
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Notes (normally open, locked, etc.)
This helps new techs, outside contractors, and emergency response.
Stock vs custom tags for HPS and LPS
Stock Valve Tags (fast + standard)
If you want a clean and quick setup for common steam systems, stock tags are the easiest way to start.
Stock Valve Tags: https://printproaz.com/collections/stock-valve-tags
Custom Valve Tags (your format)
If you need:
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a special numbering format
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extra text
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building codes or equipment names
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different abbreviations
…then go custom.
Custom Valve Tags: https://printproaz.com/collections/custom-valve-tags
Quick checklist: labeling HPS vs LPS the right way
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Identify your PRV stations
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Tag the inlet side as HPS
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Tag the outlet side as LPS
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Tag branch isolation valves based on which system they’re on
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Create a simple master list and keep it updated
Final tip
If your tags are clear, your steam system is easier to service. Using HPS and LPS removes confusion and helps your team work faster and safer—especially around PRV stations.
If you want to start with standard tags, use Stock Valve Tags. If you want your own format, order Custom Valve Tags.