Taco 571 Zone Valve Issue


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Old 11-08-12, 07:38 AM
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Taco 571 Zone Valve Issue

I have a Taco 571-2 zone valve that's been giving me trouble. Initial complaint was that the heat won't shut off. So I did some basic troubleshooting, and everything electrical checked out OK.

After some further inspection, it looks like the problem may be mechanical in nature.

In a nutshell, the zone valve will not stay completely closed when the head is attached to it. No matter what I try, if the head is attached to the valve body, the hot water flows. I've already tried replacing the head with an exact model (even the same late 80's vintage) and the valve still doesn't want to close.

On the other hand, when I remove the head(s), the zone valve will then shut off completely, and no hot water flows.

The zone valve is not "stuck" in the traditional sense, since I'm able to push the plunger down (using some large pliers) and then release it. However, the plunger motion itself does seem a little "sloppy" compared to another spare Taco 571 that I have on hand.

Based on my observations, I'm thinking that the problem is in the valve body, like maybe a weak spring or something like that.

What do you guys think?
 
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Old 11-09-12, 07:55 AM
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Poking around the internet, I see that there is a "Valve & Seat Assembly Repair Kit" (# 571-004RP) available for the Taco 571 zone valve.

So, if the Taco 571 valve body is indeed repairable, then couldn't I just remove the same "kit" elements from a spare 571 that I have lying around, and then use those elements to repair the faulty 571 that is currently giving me trouble?
 
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Old 11-13-12, 05:22 PM
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So, if the Taco 571 valve body is indeed repairable, then couldn't I just remove the same "kit" elements from a spare 571 that I have lying around, and then use those elements to repair the faulty 571 that is currently giving me trouble?
I believe the answer to my own question is "yes", although unfortunately I cannot 100% confirm this for sure.

Yesterday I took apart the spare 571 valve I had, and indeed the internal elements are (or at least appeared to be) identical to the "valve and seat assembly" shown in the repair kit that I linked to above. So figuring I was good to go, I then I tried to take apart the malfunctioning 571 in the same way , so as to effectuate a swap of the components. Unfortunately, it was a "no go".

As much as I tried, I could not remove the valve/seat assembly from the malfunctioning 571. In fact, it would not budge at all. Whereas the assembly easily popped out of the spare 571, it was the complete opposite experience regarding the malfunctioning 571. I tried some penetrating oil, prying it out with a screwdriver, etc. but to no avail. It was at that point that realized that, even though I had earlier been able to press the plunger up and down using a pair of large pliers, the valve/seat assembly itself had not been moving up and down accordingly.

Bottom line: the malfunctioning 571 was complete toast. I ended up having to cut out the entire valve and then sweat in the spare (much easier said than done, believe me - the valve is located on the baseboard piping, in the corner of a bedroom, with virtually no play in the piping.) I of course then tested the replacement 571 for leaks and for proper operation, and everything checked out fine. The apartment unit now has heat that turns on and off according to the t-stat, just like it’s supposed to.
 
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Old 10-21-13, 08:09 PM
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Haven't seen this forum before, but happened to find your thread about the Taco 571. I have a problem similar to the one you had, but in my case the 571 is allowing flow when another zone is on, but the problem ZV is off. In fact, I've actually removed the power head and this valve still flows. And I've also worked the plunger with large pliars, and flow doesn't stop even though the plunger looks to be correctly in the closed/up position. So it's definite that something is wrong with the innards of this 571.

I was going to drain the system and replace the spring and plunger assembly with ones from a new 571, but then I saw your post. The gasket which makes the watertight seal is rubber, and the lower spring just sits free in the bottom of the valve body, so I'm having a hard time understanding why the rubber gasket and plunger wouldn't just pop out after you removed the 4 screws holding the metal cover plate on. After you cut out the old ZV, did you happen to force it open, in order to see why it was so stuck and wouldn't come free?
 
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Old 10-22-13, 11:24 AM
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After you cut out the old ZV, did you happen to force it open, in order to see why it was so stuck and wouldn't come free?
I unfortunately did not determine what caused the problem with that 571. It's really anyone's guess. Even after I had the unit removed and on the bench in a vise, I still couldn't get the thing apart with regular hand tools. So I ended up just tossing it into my scrap bucket. By then it had already taken up enough of my time.

I say go ahead an try doing the swap. Maybe you can be the one who confirms that it's possible to repair one 571 with parts from another 571 (albeit under circumstances different than mine). Let us know how things turn out for you.
 

Last edited by Rockledge; 10-22-13 at 11:40 AM.
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Old 08-04-14, 07:52 PM
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Well, better late than never. The 571 zone valve having the problem that I described above controls a Superstor indirect tank. The DHW in the tank was getting "over" heated whenever one of the HW zones ran. I didn't get a chance to get to the ZV last year, so during the heating season we needed to be careful about the erratic extra-hot HW temps. But with no small children in the house, it wasn't a real big deal. I was finally able to get this job done on Sunday.

The valve and spring assembly did pop out with almost no effort at all. Once it was out, what I found was that a small (3/4"x1/4") piece of plastic had become trapped at the top of the lower spring, and part of it had permanently wedged in a position that blocked the valve from fully closing shut. There was nothing torn out of the valve itself, and I have no idea where that plastic came from. A guess would be the HVAC guy who did the job originally might have gotten careless and let that bit of debris drop into a pipe. I gave some thought to reinstalling the original ZV assembly and returning the one I bought, but decided that 23 years of service was enough. I was not up for refilling, bleeding, and then finding a leak from the old worn gasket and doing everything a second time. Happy to say that, in my case, the valve inner assembly replacement was a very fast and simple job.
 
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Old 08-05-14, 12:21 PM
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Interesting... you may never know where that plastic part came from.

Stranger things have been found... potato chip bags f'rinstance.
 
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Old 08-05-14, 05:36 PM
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Good to know that Taco 571 inner parts are replaceable. Thanks for the feedback.
 
 

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