The quick answer
The USG 143-1 and 143-2 are the same regulator. The only difference is the internal relief valve (IRV): the 143-2 has one, the 143-1 doesn't. For most residential service, you'll spec a 143-2 (the version Holland stocks), then make two configuration choices that actually determine fit — a spring sized to your outlet pressure (a Blue spring covers the typical ~7" w.c. residential target and caps the outlet at a safe level) and an orifice sized to your inlet pressure and load. "Which 143 fits my application" is really a question about getting the spring and orifice right, not about choosing between different models.
If that's all you needed, the rest of this article shows you how to make those choices without guessing — and the one mistake that puts a regulator on a meter set undersized.
First, let's clear up the part number
The 143-80 is the model number. The suffix on the end is what tells you the configuration — specifically, whether the regulator includes an internal relief valve, and in one case a low-pressure cutoff:
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143-80-1 — no internal relief valve
-
143-80-2 — internal relief valve included
-
143-80-6 — internal relief valve and low-pressure cutoff included
Everything else — body, springs, orifices, internal parts — is shared across them. So "which 143" comes down to reading that final digit: it's the only thing that changes the configuration.
What the USG 143 actually is
The 143 is the workhorse service regulator for residential and light-commercial gas service. It's a single spring-loaded platform that you configure for the job in front of you. Three decisions do all the work:
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Internal relief valve — do you need one, and will it actually protect at your conditions? (This picks the suffix: -1 for none, -2 for relief, or -6 for relief plus a low-pressure cutoff.)
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Spring — sets your outlet pressure.
-
Orifice — sets the maximum inlet pressure the regulator can handle, and caps how much gas it can pass.
There's also a High Pressure (HP) version of the -2 for applications that need a higher-pressure spring. We'll cover that below.
Get those right and the 143 does its job for decades. Get the orifice wrong and you'll be back at the meter set explaining why the furnace won't fire.
Decision 1: Do you need internal relief? (143-1 vs. 143-2)
The internal relief valve is a form of overpressure protection built into the regulator. On the 143, it's designed to vent excess gas when the outlet pressure climbs to roughly 9" w.c. above your desired setpoint — bleeding off pressure before it can reach downstream equipment limits.
Because the -1 and the -2 are otherwise identical, the default move is straightforward: spec the 143-2 and get the relief protection — as long as the IRV will actually provide protection at your application's conditions. That's also the version Holland stocks, so it's the one you can have shipped the same- or next-day.
The catch that trips people up: having an IRV does not automatically mean you have overpressure protection. The relief valve's behavior depends on your specific inlet and outlet conditions, and even a regulator with an IRV may not provide protection in every scenario. Before you rely on it, check the IRV chart on the data sheet for the regulator at your conditions. This is the single most overlooked detail on the 143 — the assumption that "it has a relief valve, so I'm covered." Sometimes you are. Sometimes the chart says otherwise.
For a deeper look at how relief and lock-up behavior work together as a safety system, see our explainer on service regulator lock-up pressure and our comparison of internal vs. external relief regulators.
Decision 2: The spring sets your outlet pressure
Your outlet pressure is determined by the spring. Pick the spring whose range brackets the delivery pressure you need:
|
Spring color |
Outlet pressure range |
Notes |
|---|---|---|
|
Red |
3.5 – 6.5" w.c. |
|
|
Blue |
5 – 8.5" w.c. |
Typical residential — caps the outlet in a safe band |
|
Green |
6 – 14" w.c. |
For outlets above the Blue range |
|
Orange |
12 – 28" w.c. |
|
|
Black & White |
0.5 – 2 PSI |
|
|
Cadmium |
0.5 – 2 PSI |
143-2HP only |
|
Black |
2 – 6 PSI |
143-2HP only |
For most residential service, the target outlet pressure is around 7" w.c., which makes the Blue spring (5–8.5" w.c.) your starting point. There's a safety reason to prefer it: because the Blue spring tops out around 8.5" w.c., a technician in the field can't dial the regulator up to an unsafe delivery pressure the way a wider-range spring would allow. It brackets the residential target and caps the ceiling at the same time.
Step up to the Green spring (6–14" w.c.) only when the application genuinely needs an outlet above the Blue range, and to the higher-pressure springs only when delivery pressure climbs further still — noting that the two highest-pressure springs (Cadmium and Black) are only available on the High Pressure model.
The springs are identical across the -1 and the -2, so this choice is independent of whether you went with internal relief. Once you've picked it, adjusting the outlet pressure to your exact setpoint is a quick field step.
Decision 3: The orifice sets your inlet ceiling — and your capacity
The orifice is where most sizing decisions are won or lost. Each orifice has a maximum allowable inlet pressure (MAOP), and your inlet pressure must not exceed it:
|
Orifice size |
Max inlet pressure (MAOP) |
|---|---|
|
1/8" |
125 PSI |
|
3/16" |
125 PSI |
|
1/4" |
60 PSI |
|
5/16" |
40 PSI |
|
3/8" |
40 PSI |
|
1/2" |
20 PSI |
|
5/8" |
10 PSI |
Notice the inverse relationship: the larger the orifice, the lower the inlet pressure it can hold. A 1/8" orifice handles up to 125 PSI; a 5/8" orifice tops out at 10 PSI.
Here's the tension you have to manage. A larger orifice passes more gas (more capacity), but it also limits how much inlet pressure you can run. A higher inlet pressure increases the flow you can push through a given orifice, but it also forces you toward the smaller orifices. So you can't simply pick the biggest orifice for maximum capacity — your inlet pressure constrains the choice. Final capacity for a given orifice at a given inlet pressure comes off the capacity table on the data sheet (or a quick call to our applications desk).
The most common 143 mistake
The single most common error we see is selecting an orifice that leaves the regulator undersized — too small to pass the gas the application actually needs. When that happens, the regulator can't deliver enough volume, and the downstream appliance doesn't operate correctly. It's a quiet failure: everything looks installed and fine until the load shows up and the equipment starves. Sizing the orifice to the real peak load — and verifying it against the capacity table — is what prevents the callback.
Standard vs. High Pressure (HP)
The 143-2HP is the same regulator built to accept the higher-pressure springs — Cadmium (0.5–2 PSI) and Black (2–6 PSI) — that the standard model doesn't offer. If your application needs an outlet pressure above what the standard springs provide (roughly above 28" w.c. into the PSI range), you're looking at the HP model. If you're in the standard residential 6–14" w.c. band, you don't need it.
Putting it together
|
Decision |
What drives it |
Residential default |
|---|---|---|
|
-1 vs. -2 |
Need for internal relief (and whether the IRV chart confirms protection) |
143-2 (Holland's stocked version) |
|
Spring |
Required outlet pressure |
Green (6–14" w.c.) |
|
Orifice |
Inlet pressure (MAOP) + required capacity |
Sized to load; verify on capacity table |
|
Standard vs. HP |
Whether you need a high-pressure spring |
Standard |
Because the -1 and -2 share all internal parts, springs and orifices are interchangeable between them — the only thing to confirm is whether you're working with a standard 143 or the High Pressure model.
Three worked examples
Example 1 — Single-family home, standard distribution. Inlet pressure 2 PSI, outlet target around 7" w.c. The Green spring (6–14" w.c.) covers the outlet. At 2 PSI inlet, every orifice clears its MAOP, so inlet pressure doesn't constrain you here — choose the orifice that passes the home's peak load and confirm it on the capacity table. Spec the 143-2 and verify the IRV chart shows protection at these conditions. Result: 143-2, Green spring, orifice sized to load.
Example 2 — Higher inlet-pressure service. Inlet pressure 60 PSI, outlet target around 10" w.c. Green spring again for the outlet. But 60 PSI inlet means the orifice MAOP must be at least 60 PSI — which leaves you only the 1/4" (60 PSI), 3/16" (125 PSI), or 1/8" (125 PSI). Everything 5/16" and larger is out. Your maximum capacity is now capped by what a 1/4" orifice can flow at 60 PSI, so check the capacity table carefully; if the load exceeds it, the 143 may not be the right tool for that service. And pay close attention to the IRV chart here — at elevated inlet pressure is exactly where "it has an IRV" doesn't guarantee protection. Result: 143-2, Green spring, orifice no larger than 1/4", capacity verified.
Example 3 — Elevated outlet pressure. Outlet target 2 PSI. That's above the Green range, so you move to the Black & White spring (0.5–2 PSI) — which is available on the standard 143-2, no HP model required. But if the target were instead 5 PSI, you'd need the Black spring (2–6 PSI), which is HP-only, pushing you to a 143-2HP. Lesson: the outlet pressure can quietly decide whether you need the standard or HP model.
Common mis-specs and how to avoid them
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Undersizing the orifice. The number-one field problem. Size to the real peak load and check the capacity table before you order.
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Assuming the -2 always protects. The IRV chart, not the part number, tells you whether you have overpressure protection at your conditions.
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Wrong spring for the outlet. Match the spring range to the delivery pressure you actually need — don't default to Green if the application calls for something else.
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Forgetting the HP model. If your outlet pressure needs the Cadmium or Black spring, the standard 143 won't get you there.
Spec it once, get it right
The 143-1 and 143-2 aren't really competing models — they're the same regulator with one difference. The real work is configuring it: relief, spring, and orifice, matched to your inlet pressure and load. Do that, and the 143 is exactly the dependable, decades-long service regulator it's known to be.
Need a 143-2 — or help confirming the spring and orifice?
Holland Supply stocks the USG 143-2 along with the full range of springs and orifices, ready for same- or next-day shipping across Ohio and surrounding states. If you'd rather have a second set of eyes on the inlet pressure, load, and IRV chart before you commit, our applications team will size it with you.