Guide
Which Steam Vent Do I Need
One pipe steam, plain English, in about four minutes.
4 min read · First Ave Supply, 1587 First Avenue
Most prewar buildings on the East Side run one pipe steam. One pipe in, no pipe out, and the air has to get out of the radiator before the steam can get in. That is the vent's whole job.
If a radiator is cold, or hot at the wrong time, or hissing and spitting, the vent is usually the reason.
Two questions decide everything
Where does it screw in? Into the side of the radiator near the top, or into the top of the steam main down in the basement. Those are two different parts. Radiator vents are small. Main vents are big.
How fast should the air come out? This is the part almost nobody gets told. The radiator closest to the boiler fills first and the one at the end of the line fills last, which is why the apartment at the end is always cold. You fix that by slowing the near ones down and speeding the far ones up. That is called balancing, and it is done with vents, not with the valve.
Radiator vents
These screw into the side of the radiator. Bring the old one and we match the thread.
| Model | Thread | Adjustable |
|---|---|---|
| Hoffman 40 | 1/8 angle | No, one fixed rate |
| Hoffman 41 | 1/8 straight | No |
| Hoffman 43 | 1/4 straight | No |
| Hoffman 508 | Convector, moisture type | No |
| Gorton 4, 5, 6, C, D | 1/8 and 1/4, angle and straight | Rate is chosen by model |
The Hoffmans are one speed. Good, simple, right for a radiator that already works. Swap it and move on.
The Gorton number is the speed. This is the one thing worth remembering.
#4 #5 #6 C D
slower ──────────────────► faster
Radiators near the boiler take a slower vent. The ones farthest away take a faster one, so the whole line fills at about the same time. A building with a permanently cold end apartment is usually a building where every radiator has the same vent.
Main line vents
These go on the steam main in the basement, not on a radiator. They are much bigger and they do much more work. Venting the main properly is the single biggest improvement most buildings can make, and it is the step most often skipped.
| Model | For |
|---|---|
| Hoffman 45 | 1/2 female by 3/4 male, convector and main |
| Hoffman 75 | Low pressure main |
| Hoffman 76 | Vacuum systems, medium and large mains |
| Gorton 1 | Main vent |
| Gorton 2 | Large capacity main, long runs |
Install a main vent 6 to 10 inches above the horizontal return and at least 18 inches above the boiler water line. Lower than that and it sputters water or gets hammered.
The three problems and what to do
One radiator never gets hot and it is far from the boiler. Faster vent on that radiator. Gorton D or C. Then check whether the main is vented at all.
One radiator gets too hot, too fast, and it is near the boiler. Slower vent. Gorton 4 or 5.
It hisses, spits or leaves water on the floor. The vent is stuck open or the radiator is pitched wrong. Replace the vent first, it is the cheap answer. If it comes back, the radiator needs to pitch back toward the valve.
What not to do
Do not close the supply valve halfway to slow a radiator down. On one pipe steam the valve is open or closed, nothing in between. Half open traps condensate and that is where the banging comes from.
Do not put a 1/4 vent in a 1/8 tapping with a bushing and call it done. It will work, but you have changed the venting rate without meaning to, and you will chase that radiator all winter.
Bring the old one
Thread size is easy to get wrong from memory and impossible to get wrong in person. Pull the old vent, put it in your pocket, bring it to 1587 First Avenue. We match it at the counter and you leave with the right one.
Shop this guide
21 itemsPrices shown are register prices. Sign in to see your account pricing.
More guides
- What Ice Melt Does to Concrete, Floors and Your LiabilityWhy the cheapest rock salt costs a building more than it saves: spalling, ruined lobby floors, dead tree pits and slip and fall exposure.7 min read
- Safe Step Ice Melt, Which Bag for Which JobWhich Safe Step bag suits a sidewalk, a garage ramp, a roof or a pet area, with the working temperatures from the product data.4 min read
- Ice melt before the first freezeBuy it in October. Four minutes.4 min read
- NYC Trash Containerization Rules, and Which Bin You Actually NeedWho needs the Official NYC Bin, who can use any rigid 55 gallon container, set-out times, and what to buy for a 12 unit versus a 40 unit building.5 min read
- Can liners explained, which bag your building actually needsMatch liner dimensions, mil thickness and color to office cans, Brute containers, recycling stations, compactors and renovation debris.3 min read
- Which garbage bag do you use?Size by can, not by guess.4 min read
- Basement and closet lightingPorcelain keyless, pull chain sockets and the flush mount that replaces a bare bulb. The unglamorous fixtures that run a building.4 min read
- Batteries at the counterNine volts for smoke detectors, coin cells for the key fob, and why a building buys the sixteen pack.3 min read
- Drain daySlow, stopped, or the whole line. Three different problems.4 min read
- The turnover electrical kitWhat to buy once so the apartment is done in one trip.4 min read
- Toilet seats and bathroom turnoverRound or elongated, and the three numbers that decide it.3 min read
- Benjamin Moore at First AveAura, Regal Select, Advance, ben and Super Hide. Which line belongs on which wall, and which one a building actually buys.5 min read
- Paint prep, the painters kitEverything that goes in the bag before the paint does. Tape by surface, cloths by weight, grit by coat.4 min read
- Patch, fill and glueSpackle, joint compound, plaster of paris and the glue that actually holds. What to use on which hole.5 min read
- Roller liners and traysNap thickness by surface, liners by the sleeve, and why a metal tray outlives six plastic ones.4 min read
- Taping knivesWhich blade for which job, from the dollar plastic scraper to the fourteen inch skim blade.4 min read
- Hang anything without calling the superPlaster, lath, brick or tile. The wall decides, not the hook.4 min read
- High security compared, Mul-T-Lock, Medeco, MarksWhat restricted actually means, and what a building is buying.5 min read
- Mops, brooms and the janitor closetWhat a porter actually uses every day, and the difference between a house broom and a lobby broom.4 min read
- Padlocks and lock boxesShackle size, keyed alike, and the lock box that lets a contractor in without you being there.4 min read
- The NYC pest kitGlue boards by the case, bait where it belongs, and the foam that ends the mouse problem for good.4 min read
- Window washingOne pass, top to bottom, wipe the blade. Why paper towels leave streaks and a squeegee never does.3 min read
- The odd bulb wallAppliance bulbs, night lights, circline, bi-pin and candelabra. The bulbs the big stores stopped carrying.4 min read
- Window guardsThe January notice, and what actually satisfies it.4 min read
- Birch or CDX, and Which Sheet Your Job Actually NeedsCDX by the sheet plus a cut charge, birch by the square foot, and the point where buying the whole sheet is cheaper than buying the cuts.6 min read
- Getting Sheetrock Into a Manhattan Walk-UpWhich board to buy, what fits the elevator, and what to have ready before the truck arrives at a walk-up.6 min read
- How Same-Day Delivery Actually WorksThe cutoff, the rates, and what happens when an order mixes shelf stock with next truck items.5 min read
- Gloves by the dozenNitrile by the box, coated knit by the pair, and what a building should keep in the closet.3 min read
- Scotch and 3M tapes by jobDuct, electrical, foil, thread seal and mounting. Which tape belongs on which job, and the three places people use the wrong one.4 min read
