wet return replacement

Polycarp

Hello all.  I am about to embark on the last stage of my boiler rehab, so I thought I'd run my plan in front of brain trust before I start cutting pipes.



The system was installed about 100 years ago.  So far, I have replaced the boiler and all near-boiler piping, replaced all the radiator valves, replaced all of the radiator vents, refinished the radiators, added main vents, insulated the mains, replaced the main drip, and de-knuckleheaded some of the main piping.  The (hopefully) last thing to do is to replace the wet return (you know, the one I should have replaced when I replaced the boiler).



So here's my plan:  replace the whole wet return with new pipe.  OK, it's a bit more complex, so I have some specific questions, and I've attached some crude sketches.



I want to put isolation valves on all the drips (see sketch of generic drip) and a hose bib at the far end of the return so that I can flush the gunk out of the wet return periodically (remember, 100 year-old mains).  I've heard unions should be above the water line, what about full-port valves?  Is there a reason to put them above or below the water line?



I'll be rerouting the wet return to work better with my boiler (the old boiler had the return on the other side).  So this raises the question of where to put the water feed.  Should I put it on the boiler side of my Gifford Loop (yep, went with the Gifford), or the wet return side.  The install manual has it on the wet-return side, but that makes my auto-fill a convenience item instead of a safety item (well, it's a rental, so maybe it is a *bit* of a safety item, and convenience is pretty big for a rental).  So which should I do?  If I go boiler-side, does the location I indicated boiler side work (see yellow dot on sketch of near-boiler piping)?  If it is wet return side (see third sketch), is 3' away from the boiler too far away if I want to ensure that new water actually gets boiled and de-oxygenated?  (It would certainly prevent thermal shock.)





As always, thank you all so much for your help.  It has been invaluable so far.

gerry gill

Where you want to put

the water feed should be okay..i would probably put it into the wet return but for no other reason than because i always have ..you could put the union and ball valve anywhere you want to without harm.

Charlie from wmass

I like to put the water

on to the boiler side of the return line inside the hartford loop to make sure the water does not sit in the return with out being boiled first. But that's just me. I also add a globe valve I keep throttled so the manual feed can not be opened wide without doing it on purpose.

Polycarp

globe valve

So that location just below the boiler tapping and just above the mud leg looks fine to you?



I thought of putting a valve that could throttle the flow on my feeder. Is there a reason to use a globe instead of a ball or gate? I only ask because I already have a full port ball valve in my feeder array and would much rather just use it.



Thanks for your comment.

Hap_Hazzard

ball/gate/globe

Gate valves are notorious for getting junk stuck under the gate, keeping them from closing all the way, and on a water feed line, you'd never see it leaking, you'd just wake up to a cold house and a flooded boiler (or, in your case, an irate tenant).



Ball valves work great as shut-off valves--rarely leak, you can tell at a glance if they're on or off--but they're kind of an on-off switch--not so great for throttling. That's not a real problem on a water feed line except that they tend to cause a little water hammer when you shut them off; but then, your auto-feeder is going to do the same thing anyway. If that bothers you, you'll want to put an arrester on the line, and that should take care of both.



I have a ball valve on my water feed line where it comes off the water main so I can turn it off for the summer or if it starts leaking or whatever, then I have ball valves to isolate the water feeder, as recommended in the manual, then a gate valve for bypass. I thought I could get away with a gate valve because I didn't think the crud would back up that far into the water line. I was wrong. Now that I've taken it apart and seen for myself, I'd recommend using a globe valve, like Charlie says.

ChrisJ

valves

I went with two ball valves in series when I did mine.  No auto feeder and I keep one valve which is out of the way almost completely closed which is what throttles the flow.  I have no problem controlling the ball valve but I wanted another one out of the way to do it in case I'm away and the wife has to add water or something.  It also gave me the ability to shut a second valve incase one starts leaking.  The way I set the one valve is by opening the one closest to the boiler fully and then slowly cracking the second one open until its where I want it and then it gets left there.





Also remember to use a backflow prevener, preferbly one rated for above 212F or you will also need to use a check valve in some areas.

Polycarp

valves

I have the auto-feed array that includes a two isolation valves for the auto-feed and a valve in the bypass.  I may end up just throttling one of the isolation valves.  Luckily the auto-feeder has a built in check valve, so I at least save myself that trouble.

Polycarp

wet return side

I'm leaning toward the wet return side just because that is what is in the manufacturer's diagram, and despite my use of a Gifford instead of a hartford loop and my addition of a mud leg at the bottom of the boiler return, I think there's a value in having the thing look as much like the diagram as possible .. especially with the home inspector or insurance agent comes by.