Rushing Water/Pressure Question

Howdy,

Long time lurker, first time poster.

First of all, thanks for all the help this site has been to me. I appreciate the wisdom here.

I've seen threads with similar problems, but none exactly like the one I'm experiencing. I've employed contractors to look at this issue, but have spent lots of money without any real solution, so maybe it's time for me to take this on myself.

I have a 44 year old residential gas-fired boiler which heats the original part (1800 sq. ft) of our 44 year old home. Copper baseboard radiators, one zone...house is one level ranch.

I feel the system has been maintained pretty well over the years. Each year I clean out the burners, clean the fill valve/pressure reducer filter, oil the pump, etc.

My question is, for the past few years, the unit seems to have to operate between 25 and 28 pounds of pressure (hot) to NOT hear water rushing in the radiators from time to time. I think this is an accurate reading - two gauges have told me this.

I know that the pop off is a 30# valve, and from what I read, you really should not have more than 20 or so pounds of pressure in the system when hot, but when I lower the pressure, I always hear the water.

Am I missing something - some setting or adjustment in the expansion tank maybe? There are no leaks that I can find anywhere.

I'd appreciate any counsel, and I'll happily supply any more information if someone can address this.

Thanks!

Daryl

 

I suspect that there is air in your system. By jacking up the pressure, the air compresses and makes less noise.

Have you tried bleeding air from the system? If you have a bladder-type expansion tank, are your automatic air vent(s) working, and they don't have their caps screwed down?

 

I've bled and bled from the radiators and from the cast iron air trap on the tank. It has a manual bleed and not an auto bleed vent.

 

Do you have a conventional steel exp tank, usually hanging from joists above the boiler? I'm unsure what you mean by "the cast-iron air trap on the tank" - it may not be the place to bleed air from. Please post some photos of your system so we can verify what you have. http://forum.doityourself.com/electr...your-post.html

 

Thanks - I'll take the pics tonight and post them.

What I mean is the air separator that is installed in the water line above the tank. It has no auto bleeder valve though, just a manual one.


I have as new bladder-type tank that was installed last year.

 

A system with a bladder-type tank needs an automatic air vent valve. Did your flow noise start after the exp tank was replaced? What kind of tank did you have before?

Whenever you bleed, fresh water full of disolved or entrained air is added to the system - so you wind up with air in the system even if you bleed until the cows come home - it's never ending. Without an automatic vent valve, there is no place for the air to go. An auto vent valve should have been installed when your tank was replaced a year ago.

We'll wait for photos.

 

Here's the pictures. Does this tell you what you need to know? If not, I'll take more.

 

Are you saying, Mike, that an auto vent should be installed on that rusty air separator instead of a manual bleed valve?

To answer your questions:

It's done this for a few years, with old and new tanks.

The previous tank was also a bladder tank, but much smaller and hung off the bottom of the air separator.

 

Good Grief! That system handles just 1700 sq ft? How big is that gas-fired water heater, 100 gal? And the expansion tank looks like it ought to handle a whole apartment house. But I digress.

I don't see an automatic air vent valve anywhere in the pix. Look around though - they look like this, although there are different styles: [in the 'Maid-O-Mist brand, I believe the #67 is the one you want - NJT edited this]


image courtesy maid-o-mist.com

The first place to put one is in place of the manual air bleeder on the air scoop. Make sure you get a vent with the same size pipe connection.

From your lack of valving, it looks like you may have to drain down the system to install the air vent. Or, maybe you can just completely cool down and depressurize the system, and replace on the fly, working very fast? But either way, while the system is depressurized, check the pressure in the expansion tank's air side. Pump up to about 12-15 psi if it's low.

What is that open ended black pipe pointed downward? I suspect it is the relief valve discharge, in which case it must be extended down to within 6" of the floor. The firemen will thank you when they are called to your house with the basement full of steam.

That 120-V romex wiring dangling in midair to your relay is not kosher, and should be replaced. Whover did that has little appreciation for electrical construction standards. I don't like the short length of romex going from the relay box to the transformer. It doesn't have a romex fitting where it goes into the boxes, and shouldn't be romex anyway - see how the pump is wired up?

 

Yes, unless you have found one not shown in the pix. Don't worry about the rust.

 

I would say to put one there even IF you have found another. Being an AIR SCOOP, that is a likely location in any case!

Maid-O-Mist has a nifty little device they call the 9AS 'shortstop' ... this little critter:



is a spring loaded doo-hickey that has a sealing washer on the bottom of it. It screws into the air scoop first, then the MOM goes on top of it. When you screw the MOM in, the stem pushes it open. This allows you to change the air vent easily... you still have to drop the pressure, but you won't lose much water... it's the extra 'thumb on the hole' that will save you time.

 

Seriously, what will they think of next? I wasn't aware of those. Those gadgets might work ahead of a pressure gauge - would save a shutoff ball valve.

Interestingly, the Maid-O-Mist company got its start at Niagra Falls, NY (American side), where they are still headquartered and operate tour boats (originally steam powered). Their air vent factory is located in Chicago, which is why that is stamped on the side of the can. Little known fact.

 

In addition to the stuff that Mike pointed out, I would pay some attention to the vent hood above the boiler ... make sure it's all secured properly, and LINED UP... that thing is all caddy-wompus... looks like it's ready to fall off...

What are the drip marks from that are running down the side of the boiler?

 

That really is one honkin' big expansion tank! Why ?

 

Water leaks???????????????

[wi5e-a55 youngun! - NJT]

 

Now that we're piling on...there is galvanized pipe supplying gas to the boiler. Conventional wisdom is that black pipe should be used for natural gas - supposedly, the zinc reacts with the the sulfur in the gas, causing corrosion. Most (if not all) experienced plumbers use black pipe for natural gas.

And there is copper tubing supplying gas to the water heater. My understanding is that copper is OK for propane, but not natural gas.

Who have you been using for your plumbing and heating? Let me guess: your brother in law who is hoping to start a business?

 

The pics may make the system look bigger than it is. The crawl space is 5' tall max. The boiler itself is under 3' tall.

When they installed the new expansion tank, I thought it seemed a little big, but they're the professionals, you know? It's at least 5x bigger than the one it replaced.

There is absolutely no auto-bleeder anywhere down there. BTW, when I went down to take the pics, I bled another full "scoop" of air out of that separator.

Since it's supposed to be 5 degrees tonight, I think I'll wait a few days to cool down the system. With parts in hand (and I'll definitely get one of those little shortstops too - pretty cool!) I think I can change it out on the fly.

Yes, that black nipple is the drop from the pop off. I'll extend that to 6" off the floor...and I can take care of all that electrical stuff too. The wiring was all like that when I bought the house twelve years ago, and it's one of those things...even though it's not good and I know it, it works and so...there it still is.

I'll double check, but the hood seems tight and secure, really...and straight.

I don't know about all the marks down the side of the boiler - maybe from water leaks from the past. It's not leaked since I've been here. It is over 40, as I am. I should look that good.

So, for now, the conclusion is that the pressure increase needed to quiet the thing is just a symptom of too much air still in the system and no efficient bleeding mechanism? By installing the auto bleeder (or by stationing my oldest son in the crawl space with a screwdriver for the next few months ) the air should be able to be extracted and the operating pressure reduced?

 

No, my 7 year old son.

Pile away - this is all very helpful.

All that stuff you mentioned was like that when I bought the house.

 

And in the process, you added even more air to the system. Read back over our previous posts, and try to understand the fallacy of your thinking.

 

Yes, yes, yes. Evidently, since you seem to be repeating the same question over and over, you either don't undersand or don't believe. Why not? Please explain your doubts. Or else call in somebody you trust - preferably not the guy who has been doing your work.

 

Yeah, I think once you get the auto bleeder on there, the air should gradually disappear.

The one upside to the large expansion tank is that you might never have to check or adjust the air charge in it! it could probably lose almost all it's air and still have enough expansion room... BUT, DO check it at least every two years or so... it will last longer because the rubber bladder won't get all stretched out and break.

Remember that in order to check that air charge, you must drop the boiler pressure to ZERO. You will NOT get an accurate reading of the air charge in the tank if there is pressure on the water side. You do NOT need to 'drain' the boiler, only let enough water out to drop the pressure to zero. You might want to do this when you install the air bleeder... before you pressure the system back up. The air charge in the tank should EQUAL whatever the COLD system pressure is set to.

There IS a downside to too large a tank... it has to do with air removal... when the water is heated, you WANT some pressure increase... because hot water has less capacity to hold air in solution. With such a large tank, you will have little pressure change from cold to hot... and the air will have more tendency to come out of solution and be heard beatin' a path around your system.

But, once the air is out, it's out... as long as you don't have any leaks... so the air vent will probably take care of that.

One thing you might consider though: After the system is air-free, (or even before!) instead of running at the minimum 12 PSI, think about running the COLD pressure up to say 15-16 PSI. Since with that large tank there is little chance that you will ever approach 20 PSI, the slightly higher pressure may work better for you in terms of air removal. (remember to bump the pressure in the expansion tank if you do this)

 

Mikey, you are gonna have to explain this to me...

He took AIR OUT of the scoop by opening the manual bleed on the air scoop. How does that get air back IN to the system ?

 

Easy there Mike, I'm just trying to clarify, that's all. I want to make sure I'm understanding the theory behind the prescription here.

I really appreciate your time and expertise. I'll definitely do all you suggested - both of you. The whole system, and how it should work, makes much more sense to me now.

Thanks!

Daryl

 

I think he's pointing out the need for a continual bleeding apparatus (the auto vent), since more air came in with the water that filled the space of the air I bled out.

 

By my thinking, a lot of water came out the manual vent, either with or instead of any bit of air that coincidentally happended to be situated right smack-dab at the scoop. And then when that water was replaced by the auto fill valve, more air was injected into the system. Q.E.D.

Ddidle: when you opened that manual vent valve a few minutes ago, did you get all air, some air and some water, or all water? Your answer is important, because there may be a steak dinner riding on it.

 

No more water should have entered the system... if you've got the pressure reducing valve set up at 12 PSI, and the system as you said is running well higher than that...

I don't need the steak Mike, thanks anyway! uses up valuable space in the old beer locker.

Which, let me touch on something else I thought about after my last post.

If you DO decide to run your system at a bit higher pressure, the 15-16 I suggested, leave the pressure reducing valve set at 12 ... add the extra few PSI manually with the fast fill lever.

Another note, as the air is removed from the system, you will see the pressure drop a little over time... of course... just sayin'...

 

Trooper, OK - but a mere technicality. I can find people who will testify against you.

[I'm sure you can! There's plenty of 'em out there! - NJT]

 

I bled only air out. I closed it at the first sign of water. I got air for 3 solid seconds.

 

OK, sounds good. But you've been doing that for how many years now, and not making any progress? Where did that last air vented come from after a year of bleeding?

And even when you bleed 100% air, eventually that air has to be replaced with What? Water, combined with additional air, disolved or entrained. Maybe not immediately, but eventually - otherwise, the pressure will keep going down, right?

If you want to keep having the same results, keep doing the same thing. Otherwise, try something different.

 

Hmm. The system was completely depressurized toward the middle of the heating season last year when the tank was replaced (and a new pop off and a new pressure/temp gauge was installed.) Since it was only used a half season after all that, I'm supposing it's residual from last year. Does that sound realistic?

I mean we've bled it, but mostly through the radiators when we hear the rushing. I've only bled it at the scoop a few times.

 

Guys, this is really helpful. I've gotten more useful information here than from all the people I've had come and look at this combined. I'll install the auto vent and let you know how it goes.

Seriously, thank you both very, very much.

Daryl

 

Well, not quite realistic. Depressurizing doesn't eliminate air - if anything, it adds air. Replacing the expansion tank or the relief valve doesn't reduce air, but the replacement process can add it. Your problem isn't just a "residual from last season." From what you've said, this problem has been going on for several years.

Quit fighting the obvious, and go along the the concensus here.

 

I'm thinkin' that not only did they depressurize, but probably for the most part drained the system. There's no isolation valves and such to keep the water up in the baseboards, so they probably took out and replaced a lot of water.

The way that pipe runs over to the expansion tank, up to the ceiling and down again, what you wanna bet that pipe is filled with air too? In the absence of any other plausible explanation for where the air came from, I'm going to say that it is easily conceivable that the air IS left over from the work that was done. That and the fact that whoever installed that tank apparently didn't have a clue what the function of the tank IS, there is little doubt in my mind that they didn't spend any appreciable time PURGING the air from the system before they brought it back on line... I bet that half the system was AIR when they left.

Daryl, do install the air vent, keep the system pressure jacked to say 15-16, and sit back and enjoy a beer while the vent lets the air outta yer system. Then enjoy the quiet.

 

Thanks Trooper. I'll do it.

 

As long as air stays in the line to the expansion tank, it probably won't cause a problem. It should behave like a small, conventional exp tank's cushion. If and when the air in the line works itself out toward the boiler, it should be eliminated by the soon-to-be installed automatic air vent.

 

That 'expansion tank' sure looks like the pressure tank you'd find on a well pump setup. Who installed that thing? Seems to be somewhat 'overkill'.

 

Hey, just an update. I put an autovent on there in place of the manual bleed valve and voila - quiet.

The company that put that tank in...maybe they just had it laying around.

Anyway, thanks gentlemen, for all you're efforts. You were right on!

D-

 

Thanks for coming back and letting us know ! have a goodern! (and a few more beers!)