New steam vent still leaking lots of steam

AMBishop

I've had a problem this winter with a steam radiator system leaking a lot of steam in one room and not heating up in another. The two radiators seem to be connected in series with a pipe coming out the end of one radiator going through the wall to the supply valve feeding the next one. It is a one-pipe heating system and both have Maid O' Mist steam vents. When the first supply valve is open, the first radiator spits a lot of steam and heats up the room, but the second barely gets hot. When the first supply valve is closed, both stay cold.

A while ago, I replaced the steam vent on the first radiator, thinking that if it were closing when the radiator got hot (like I understand it is supposed to) then the steam pressure would stay high enough to feed the second radiator. But this hasn't happened; the first radiator continues to spit steam and the second only barely gets hot.

Is this a problem with the new steam valve? It is a Maid O' Mist #4, which seems to be the type I should be using. I don't understand how it could be broken already and leaking steam. Should I buy a different brand of steam valve?

Thanks for your help.

Jamie Hall

Two oneI pipe steam radiators piped in series? Um... no can do. It isn't so much a problem of getting air out of the first radiator, it's a problem of getting water out and hence steam into the second radiator. I shouldn't say no can do. There might be a way to pitch the pipe in between enough, and use a straight through valve such as a full port ball valve, on the second radiator to make it work. Sort of.

Higher pressure isn't going to help. If it won't work at 1.5 psi, it won't work.

KC_Jones

Pictures of the set up would help, but based on your description it's going to be tough to get this right, if it's even possible.

First, vents spitting water/steam is usually an issue with the system not the vent. When steam hits a vent it closes until it cools and opens again. Excess water getting to the vent can cool it, cause it to open, and spit out whatever is there, which has to be water or water vapor.

The vent you have is fine, but probably too small. The issue I'm visualizing based on your description is that you are always going to have to get the first radiator 100% hot before the second one will even see steam, and that first radiator, even when hot, will limit the second one.

So you'd need a huge vent on the first one so it fills very quickly, so the steam can get to the second. If you figure out what is causing the spitting, and use a huge vent, the likely outcome is the first room overheating and the second room heating barely adequately.

Issues that can cause vents to spit. Bad piping, either sags, or incorrect pitch. Bad boiler piping pushing water into the system. Couple those with possibly too high of pressure which will make things worse.

AMBishop

Here are some photos of the radiators.
This is the second radiator. It's shimmed up a lot to drain back towards the supply valve.

This is the first radiator. The pipe is sloped up slightly when going into the wall, so water can drain back to the first radiator.

ethicalpaul

I assume that wall wasn't there when the building was first built

KC_Jones

Those pictures confirm your description. I don't see how that will ever work properly. Each radiator needs to be fed directly from the main. Again, even if you do manage to get the second one to heat adequately, the first one is most likely going to overheat the room it's in.

As far as the spitting, I'd be looking at the feed to the radiator and the boiler piping. Bad near boiler piping, sags, or improper slope can all lead to water issues.

dko

I had someone show me a similar pic of this same exact conundrum. Owner was splitting a room in a large apartment and needed a rad in the new room. No touching the flooring or others piping. Plumber added a tee on the existing 1-1/2" riser and split the supply going right and left into each room.

In OP's case, could do the same if had room to flip the rad to the other side of the supply. Though you'd have even more wasted space of pipe running to the other room. Or instead add a side outlet elbow on the supply, change to a straight valve, and then run the pipe around the back of the rad into the other room with it's own valve keeping the pitch good. Would probably need to be on pedestals. Riser looks like 1-1/4

Of course, only if you didn't have access to add a supply from below.

bburd

Would have to check the size of the riser pipe to see if it's large enough for the total load of both radiators in square feet of EDR. If you can give us the details on both radiators and the size of that pipe we can tell you if it should be OK.

Jamie Hall

Being a contrary minded soul sometimes, have you tried the system with the vent on the first radiator completely closed? And a fairly large vent on the end radiator?

dabrakeman

..and need a constant pitch from the end of the second radiator all the way back through the connecting pipe and the first radiator.

delcrossv

@dko called it.

one of these (side outlet elbow), and fittings to get behind rad 1. Two straight type rad valves. Done.

You may be a little short on EDR, but they will both work. Everything should pitch towards the below fitting. Slow vent on first rad, faster vent on second.