Lowering steam mains

RedChops

This is a bit of a weird one. I felt like the pitch on my steam mains looked fishy so I took a laser level to them. 

I’ll set the stage: two pipe system, piped to be parallel flow, my boiler is against a wall, in the center of that wall. The mains come up, elbow to horizontal, then after some length do a 90 degree to run along the front and back walls of my house, they end up making a perimeter loop, coming back together where the mains drop to the wet return.

 On the front of my house where I have a couple problems, the pipe is actually pitched towards the boiler before it makes the turn to run along the front of the house, then runs pretty much without any pitch for half the distance. The pipe supplying the back of the house pitches away from the boiler like it should, but also runs without pitch for most of its length.

Normally I think you’d lift the pipe on the high point to pitch it correctly, but given that the pipes by the boiler are already too high I don’t really have that option. This boiler is much smaller than the original so I have plenty of room, so my thought is to instead lower the pipes to make the pitch correct. I’ve dropped the pipe hangers and the mains are completely held in place by the takeoffs to the rads and 2nd/3rd floor supplies. Maybe they’d sag on their own in 10 years. My zany thought is to use some sort of jack or something on the tees to the takeoffs to push the pipes lower. Is that a dumb idea? Is there a more sensible way to do what I’m thinking of? I’m also not sure, if I go this route, what kind of jack I’d even use. 

Jamie Hall

There is no particular harm to having part of a steam main pitch one way, and then the rest of it pitch the other.

Provided.

That at every single low point -- even if that is right at the boiler -- there is a drip to a wet return.

I'd be exceedingly cautious about trying to pull the main down much -- or up -- as that will disturb the pitch on every single runout or horizontal pipe up in the house, and you may make things much worse.

EBEBRATT-Ed

@RedChops

If your system is parallel flow the mains should be at their highest point at the boiler and pitch downward in the direction of flow.

Jacking the pipes lowere would be a bad idea you will break something and be in a worse mess.

Sometimes systems are designed to work counterflow where the condensate flows against steam but the piping has to be sized for this

RedChops

Yeah that’s a bit of the issue, the highest point of the piping on the side that’s giving me problems is actually about 7.5’ away from the boiler. From there, there’s a very slight pitch down to the first runout where it pretty much totally levels off. It’s in this level section of the mains where condensate from the mains is getting sucked up in to some first floor rads and knocking, and the second floor supply causing slow heating and water sloshing sounds in the walls. 

There are no drips to wet or dry returns at any point in this system except for the very end  of the supply perimeter. I suppose I could have somebody install them, pipe tapping is a bit outside of my toolkit. 

Maybe this one is outside the realm of DIY. 

Hap_Hazzard

How are you going to lower the pipes without pulling the radiators through the floor? Those pipes aren't going to stretch, even if you put a jack on them. You'd have to extend every riser from every takeoff from the main, and extend each one exactly enough to end up with the pitch you're trying to achieve. It's doable, but it's not a trivial exercise. You'll need to cut and thread your own nipples because you'll need very incremental lengths, and you'll need to correctly account for the length added by each union—and you'll have to use unions unless you think you can spin the risers to screw them into couplers, in which case you need to account for the length of each coupler. Sounds like fun, doesn't it?

delcrossv

@Hap_Hazzard describes the issue quite well.
We have a 2 flat with a similar problem. Decided to set the VXT to 8 minutes and be done with it, but the system is quiet.

In your case, it probably makes more sense to have drips installed than re-pitching the whole main. What diameter are your mains?

JUGHNE

If there are no steam take offs within that first 7.5' of steam main there would only be condensate water from the main itself that would be counter flowing back towards the boiler. This may not be an issue to worry about.

Actually, could you raise that point higher and have more slope towards the return at the far end?

Steamhead

If they heat quickly and don't bang, leave them alone.

RedChops

No pipe in the system is larger than 2”, the perimeter supply mains all appear to be that as well unless there’s something really dodgy going on under the insulation (jokes, nobody did anything that dumb in the history here)

I did lift the 7.5’ section as much as it would go before I hit resistance and it’s certainly a little better. It looks like when this boiler was changed out from the original in 97, the knucklehead installers not only followed exactly 0 guidelines in the book, including wiring the transformer incorrectly, they also didn’t connect the mains to the headers as high as they were originally, giving me a little slack to work with. As a ranty aside, I’m actually impressed at those installers. The book for this model called for a single 3” riser from the boiler, a 3” header, and a 1.5” drop from the header to the Hartford loop. What did they do? 2 risers, 2” everything, both takeoffs to the mains in between the risers on the header. I’m impressed the system works so well and fast in 90% of the house. Swapping the 3” for two 2”s might have worked as intended if they didn’t slam the steam together in the middle. 

This last cycle I got rid of the loudest banging radiator with a couple shims, we’ll see if it comes back next cycle. The second floor supply wall still sounds like somebody is taking a bath in it and the one slow and one cold radiators (different floors) aren’t much better, but at least there’s incremental progress. 

RedChops

@Hap_Hazzard you know, if it weren’t my house, and it weren’t winter, and I was actually getting paid for it instead of spending my own money, that actually does sound kinda fun. At least from an engineering perspective. 

ethicalpaul

Yeah that’s a bit of the issue, the highest point of the piping on the side that’s giving me problems is actually about 7.5’ away from the boiler. From there, there’s a very slight pitch down to the first runout where it pretty much totally levels off. It’s in this level section of the mains where condensate from the mains is getting sucked up in to some first floor rads and knocking, and the second floor supply causing slow heating and water sloshing sounds in the walls.

Don't be too quick to assign too much blame to this pitch issue. For years or decades I had an "uphill" pitch from my boiler to a point about 10 feet away that had the actual high point of my parallel-flow system.

I saw very little condensation ever flow back to the boiler from this short section of "counterflow". And it was certainly never picked up by the steam and carried to the radiators. Don't forget that almost all parts of a parallel flow main have condensate flowing in them and yet that is not picked up and carried up to radiators (that's why the radiator takeoffs come off the top of the main).

if you can hear water sloshing around it is likely from either an unintentional water trap due to a sag, or it could also very likely be poor near boiler piping that is causing real carryover/surging of many gallons from the boiler to the main.

How is your water level during the firing cycle?