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Old 08-05-2015, 10:57 PM   #1
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Filling and purging hydronic heaters


I have no experience with hydronic heating and this is the first house I have had this type of heat in. Doing a lot of remodeling this summer and replaced a few of the baseboard heaters while I had things apart. Now need to fill the system back up. The system has one supply and return from the boiler that branches off into zones. So what is the correct way to fill these zones and the system?

Filling and purging hydronic heaters-img_20150805_104737077.jpg

Filling and purging hydronic heaters-img_20150805_104744206.jpg

Filling and purging hydronic heaters-img_20150805_104811007.jpg

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Old 08-05-2015, 11:15 PM   #2
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as long as you have the system drained down I would install a drain valve just above the shutoff valve right above the circulator/pump on the side of the boiler. with that shutoff valve shut and the new drain valve open you can fill the system through the drain on the bottom of the boiler, push it throughout the system and drain it and the air out the new drain valve. I do this with a pump, but you can do it with a garden hose if you carefully watch the pressure in the system....... if you get too much pressure the relief valve will open and dump water and on old systems the relief valve tends not to seal back down and will leak due to dirt and junk coming out with the water.

google "purging hydronic systems"

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Old 08-06-2015, 07:06 AM   #3
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Any particular reason you would do that instead of filling with the water supply going to the boiler? There are various shut offs and drains through out the basement for the different zones if that matters.
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Old 08-06-2015, 08:10 AM   #4
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We use automatic air bleeders on most of our systems, so we just fill and wait for air to stop flowing.

I assume that you're baseboards are above your boiler? Usually the baseboards will have a bless screw. Slowly fill it, being careful of the pressure, and use the bleed screws to let the air out of each high point.

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Old 08-06-2015, 08:49 AM   #5
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So after watching some youtube videos it looks like to fill the system correctly I need to add a drain valve on my return line just before(above) the return shut off valve. Then I can shut off the return line valve, open the supply and fill with water and let the water run out of the new drain valve until all the air is out. Then close the drain valve and hopefully all is good.

I'm sure this system has been serviced a time or two before so how did they fill it without a drain valve by the return shut off valve?
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Old 08-06-2015, 04:12 PM   #6
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They used the drain cocks/valves on the zone lines.
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Old 08-06-2015, 06:11 PM   #7
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Quote:
Originally Posted by beenthere View Post
They used the drain cocks/valves on the zone lines.
I'm a little confused. There are no zone valves/drains by the boiler. The boiler is in a little utility room and there is just a valve on the supply and return coming out of the boiler. And one drain on the bottom of the return by the boiler. There are some valves/drains by where the pipes split off and go to different zones. And maybe I'm using the word zone wrong. Really the pipes just split and go to different parts of the house. There are some big pipes coming off the boiler, think 1 1/4 or 1 1/2" copper. Then split and go different directions and areas of the house and return to a common return line and back to the boiler.

So if I just hook a hose up to each drain valve I see and start to fill the system and let each drain valve run for a while, one at a time, will this get the air out?
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Old 08-06-2015, 06:24 PM   #8
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Quote:
Originally Posted by ponch37300 View Post
So after watching some youtube videos it looks like to fill the system correctly I need to add a drain valve on my return line just before(above) the return shut off valve. Then I can shut off the return line valve, open the supply and fill with water and let the water run out of the new drain valve until all the air is out. Then close the drain valve and hopefully all is good.

I'm sure this system has been serviced a time or two before so how did they fill it without a drain valve by the return shut off valve?
You can't get all the air out that way.

The highest rads/lines in the house SHOULD have bleeder valves (either manual or auto). If not then you will most likely have to install them. Fill the system up, turn on the circ pump on, open all your zones (if you have more than one) give it 10 minutes then bleed the highest rads. Keep doing that until all the air is out. You may need to do this again in 24 hours since fresh water contains dissolved oxygen and will come out at the lower boiler pressure over time.

Keep an eye on your boiler water pressure. You want to keep it up while bleeding. If it drops down too much you will start SUCKING air. Your furnace SHOULD have an auto filler/pressure regulator but if you don't or it is stuck (which does happen) you will have to add water manually during the bleed process.

Last edited by Bob Sanders; 08-06-2015 at 06:29 PM.
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Old 08-06-2015, 08:42 PM   #9
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If you don't have bleed screws/valves on the high points, like rads, then the unions near by will do. I've had to do it that way. Just keep a bucket and mop handy, as it can get messy that way even with someone helping you. (you would just crack open the union just enough for air to escape. Not completely off.)

Cheers!
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Old 08-07-2015, 04:10 AM   #10
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Quote:
Originally Posted by ponch37300 View Post
I'm a little confused. There are no zone valves/drains by the boiler. The boiler is in a little utility room and there is just a valve on the supply and return coming out of the boiler. And one drain on the bottom of the return by the boiler. There are some valves/drains by where the pipes split off and go to different zones. And maybe I'm using the word zone wrong. Really the pipes just split and go to different parts of the house. There are some big pipes coming off the boiler, think 1 1/4 or 1 1/2" copper. Then split and go different directions and areas of the house and return to a common return line and back to the boiler.

So if I just hook a hose up to each drain valve I see and start to fill the system and let each drain valve run for a while, one at a time, will this get the air out?
Post some pics of those valves.

That is most likely how it was done when they originally installed the system, and why those valves are there.
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Old 08-07-2015, 04:22 AM   #11
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Quote:
Originally Posted by ponch37300 View Post
There are some valves/drains by where the pipes split off and go to different zones.
Those might be your purge stations. Is there also a valve that you can close at each drain to direct the water flow through the radiators and not from the boiler?

That lever on top of your inlet water pressure regulator will allow house pressure and larger flow for purging. Just make sure that you flip it back down before you close off any purge valves so you don't over pressurize your system.

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