Flushing hydronic heating system - help needed, pic provided


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Old 04-10-11, 09:04 AM
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Flushing hydronic heating system - help needed, pic provided

Hi,
My last great experience on this board was ~a year ago here:
http://forum.doityourself.com/boiler...-off-days.html
where you helped me dislodge debris in my hydronic loop that was holding open zone valve(s). The problem has recurred a couple times since, and now that the weather is warm I want to flush this system and get rid of the debris.

I'm attaching a pic:


In this pic, I've used abbreviations for (probably incorrect) part names:
  • MFV - main feed valve - the gate valve for controlling the main cold feed to heating system loop
  • F - feed valve - the "flip top" auto water feed valve, shaped like a bell
  • MDV - main drain valve - at the bottom of that iron pipe, for the whole heating system
  • S1-3 - shutoff valve for zones 1-3 - gate valve in each zone loop
  • DV1 - drain valve for zone 1
  • FC1 - flow check for zone 1

Regarding flushing, I want to be sure I get all the debris out, even that which might be in the boiler part of the loop.

My initial thought of what I need to do is, for each zone, starting with zone 1:
  1. shut MFV, even though there is a backflow preventer, just to ensure nothing gets back to the domestic side
  2. shut S2 & S3
  3. connect hose to DV1
  4. open F
  5. at some point close S1
  6. at some point open MDV w/hose attached?
  7. ???

Any pointers welcome, thank you again.
-Brett
 
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Old 04-10-11, 09:59 AM
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Hi Brett, welcome back.

You are calling them 'zone valves' but they aren't. They are 'flow control' or 'flow check' valves... just so nobody gets confused.

Can you possibly get a better pic of the flow control valve? include make/model info if you can determine that from markings on the valve.

Before we go on to flushing the system, which I'm not sure is the real problem, let's first see exactly what you are working with.

While it is possible that you have debris in the system, it's not that likely that you have so much floating around in there that the valve keeps getting hung open. It might be better if the valve were disassembled and inspected and cleaned first... but some are easier than others... so let's see.
 
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Old 04-10-11, 11:08 AM
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Hi,
Thanks for the reply. Sorry, I didn't think I said zone valve? The parts ID'd in the pic as FC1 are all Taco 218 Flochek.
Thanks,
Brett
 
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Old 04-10-11, 05:13 PM
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It looks like there are three? one for each of the zones?

Are all three of them sticking? or just one?
 
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Old 04-10-11, 05:33 PM
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I believe two of them are sticking. It never seems to be the most recently added zone (basement). Not sure if it matters but the 2 that stick have a flat/blade style knob on top to open the flow check, and the newer one that hasn't stuck yet has a round knob (like a toothpaste cap). Prob just a newer generation/maybe a better design.

Btw, I notice that water is now leaking slowly (drip every cpl mins) out of the tops of the 2 guilty valves as a result of my most recent unsticking process, in which I loosen the top nut, run the circulator, and tap lightly on the valve body with a hammer. So it looks like I'll need to rebuild them anyway.

I'll get another pic of these flow checks in detail.

Thanks,
Brett
 
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Old 04-10-11, 06:00 PM
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flow check pics

Here are some pics of the flow check valves. Seems like only the middle one is seeping now, I did loosen and re-tighten the knobs this afternoon, seemed to help the far one.





To answer your previous question, yep, 3 total, one for each zone.

Thanks again,
Brett
 
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Old 04-10-11, 08:29 PM
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Doh, sorry, I did say zone valve up top...
 
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Old 04-11-11, 05:26 PM
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Brett, take a look at this PDF file. It shows a 'cutaway' drawing of the valve so you can see what's going on inside of it.

If the stem is leaking, you should be able to snug down on the 'gland nut' and compress the packing around the stem. Don't muscle it down like a head bolt on a rat motor... just a wee squeeze to compress the packing a bit. The leaks at the stem should stop. If not, I think you can remove the knob and gland nut and push a bit of packing from home depot down there and reinstall the gland nut... never done it myself, but you should be able to...

From this PDF you can see that the 'guts' are replaceable. You might even think about just taking them apart and cleaning out... if you take apart, be sure to have some way to replace the gasket... it will probably get buggered... the plug on the bottom can also be removed. At least if you do this, you can see if it's debris, or just buildup inside the valve.

I'm just not sure that flushing the system is going to help much.

Your procedure needs a bit of 'refining'... we can help.
 
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Old 04-11-11, 05:52 PM
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Thanks, but I don't see the PDF?

So to begin this work, I will need to drain the system anyway, right? I assume: shut off MFV, hose hookup to MDV, open MDV, open all flow check knobs, and let gravity do its thing?

Then I'll need to do the work, and refill the system which would be same steps as a flush/purge right?

-Brett
 
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Old 04-11-11, 06:09 PM
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This may be the PDF.

http://www.taco-hvac.com/uploads/Fil...eck101-004.pdf

If its leaking at the gland nut you could try to loosen and wrap teflon tape around the stem. Wrap it clockwise. Take a 6" piece of tape and roll it in a thread and wrap. It acts as a packing, then tighten.

Mike NJ
 
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Old 04-11-11, 06:55 PM
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Thanks Mike, I had one of those more and more frequent 'duhhhh' moments!
The teflon tape idea is good... they do also sell teflon 'string' packing material.

Brett, ya know, thinking about it a bit more, you might just want to try the flush first... heck it's a lot easier than getting those valves apart... but then, you won't know until next heating season if it worked or not!

So let's run down the flush plan...

First, shut boiler off and make sure it's below 100F, don't wanna crack the block!

You don't have to but it's a good idea to manually open the flow check valves.

Flush the zones first.

Close S1, S2, S3.

Leave MFV open, you need a source of water.

Hook a hose to DV1.

Open DV1 and pull the fast fill lever on your feed valve (F) (aka 'pressure reducing valve')

You should get a fast flow of water through the boiler, through the zone, and out the drain. Continue until you think it's clean.

Release the fast fill lever on F, and close DV1.

Move hose to DV2 and repeat above.

Move hose to DV3 and repeat above.

The idea with this is to get a fast flow of water through each zone in turn.

Move hose to MDV and repeat above.

Re-open S1, S2, S3

There's a drawback to flushing... when you restart the boiler, you are going to get a lot of air in the water as the water is heated and the dissolved air is driven out. Fresh water has a LOT of dissolved air! Be sure that the air vent on top of the air scoop is fully functional. You may have to bleed some baseboards (hopefully there are bleeders where you need them). After running the system for a while, all the air will come out. It's probably not a good idea to flush and then shut down for the season as all that fresh oxygen will be in the system corroding it all summer long. Get it good and hot several times... try to get as much air as you can out of the system before shutting it down.
 
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Old 04-12-11, 09:45 PM
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Thanks NJ Trooper for the continued help & steps and lawrosa for the PDF. I'll be trying this on the weekend when I can devote some time to it. I don't think I have bleeders on my baseboards, but I will run all 3 zones afterward.
 
 

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