1/2 9D-M3 Backflow preventer failed again

In 2005 we had an issue with the same backflow preventer valve. http://i48.photobucket.com/albums/f2...3/IMG_0859.jpg We have a bucket underneath the valve that i have now drained twice. Original post HELP!!! P-WGO-6 Weil Mclain oil boiler spewing water It appears, for us at least, that these valves last about 7 years. Is that normal? Also this time i noticed that the expansion tank appears to also be leaking. Nothing wet but it appears stained on top as if it leaked in the past. Is this a problem? http://i48.photobucket.com/albums/f2...3/IMG_1243.jpg Thank you In 2005 we had an issue with the same backflow preventer valve. http://i48.photobucket.com/albums/f2...3/IMG_0859.jpg We have a bucket underneath the valve that i have now drained twice. What did you do in 2005? Did you replace the backflow preventer? If not, now might be the time. Also this time i noticed that the expansion tank appears to also be leaking. Nothing wet but it appears stained on top as if it leaked in the past. Is this a problem? http://i48.photobucket.com/albums/f2...3/IMG_1243.jpg The tank isn't leaking - it's the pipe connections. Need to tighten the connections. If I hadda guess, I'd say that the leak at the expansion tank is coming from the left side connection to your air separator, dripping onto the valve handle, running down onto the tank. Yes, we replaced the backflow preventer in 05. Thanks Inside that thing there are basically three check valves. I haven't figured out how they actually work... though I've tried... but it seems if any one of them get a bit of 'crud' in one of the check valves, they will drip. Take a look at this and see if you can figure it out: http://media2.wattswater.com/ES-9DM3_M2.pdf The one pictured doesn't appear to be the Watts brand? Watts does have repair kits for them, and I imagine that they could be taken apart and cleaned if one were frugal enough. I always recommend rigging a hose up to the water line feeding the boiler and flushing it out full blast before installing a new 9D or regulator. If it's a continuing problem, it might not be a bad idea to add a wye strainer ahead of the stuff. Something like this: WYE050 - Hydrovalve WYE050 - 1/2 Bronze Wye Strainer (Threaded) If you decide to install a wye-type strainer, you can remove the plug and install a 1/4 ball valve for flushing and cleaining the strainer - simpler that removing the strainer. Inside that thing there are basically three check valves. I think there are only two check valves? Disassembly of a 9D would probably be very instructive as to the operation. Until I visited that Watts link, I didn't realize the 9D has a built-in strainer. I still like the idea of an upstream wye strainer with a flushing valve - no wrenches needed to flush and clean. Novice, if you phone Watts, maybe they would send you a complementary repair kit as a PR gesture? Phone, don't email. Except that I don't think the one that is installed is a Watts... Yeah... I take that back... That's a 'BBFP' and not a 9D ... I don't know what the difference is (other than the price!)... but it does appear to be a Watts. The 9D kit might not fit that one... Here's the 9D: 0061935 - Watts 0061935 - 1/2 9D-M3 Dual Check Valve w/ Intermediate Atmospheric Vent and here's the BBFP: 0063190 - Watts 0063190 - BBFP, 1/2 IPS Backflow Preventer There's a check at the inlet, the outlet, and I guess the atmospheric vent isn't really a check, but that piece does slide over the vent to close it... I did pull one apart and still don't get it. That's a 'BBFP' and not a 9D Hmm. The title of this thread calls it a 9D. Yeah... and the Watts website lists no such model number as BBFP. I wonder if it's a 'counterfeit'? No... don't think so... I found another pic of the BBFP that shows the manufacturer as Regtrol, Inc. and then found this: Watts Regulator CO also does business as Regtrol Division So... is it a 9D in BBFP clothing? same same? or different? who knows? Ouch. Sorry for the confusion. I pulled the model # from the original post. Assumed it would be the same. I just looked at what is currently installed and it is Regtrol BBFP. Is there anything special I have to do to replace this? there are cutoff valves on both sides. Is there anything special I have to do to replace this? No - there are unions on each end of the valve. Use two wrenches when loosening or tightening the unions - one wrench on the union nut, and the other wrench on the body of the valve. This will avoid putting torque on the soldered connections. Don't put pipe dope or teflon tape on the union threads. Don't put pipe dope or teflon tape on the union threads. They may be 'flat faced' unions. The last one that I replaced came with NYLON sealing washers and it was a b1tc4 to get them tight enough to stop leaking. If your replacement comes with those, you might wanna pick up some 'water meter washers' of rubber to use instead... your local plumbing supply should have 3/4 water meter washers in stock. The OD is 1.15-1.2 and the ID is 0.75 Thank you. The replacement worked out. Is there anything I can do with the old one to clean it out or recycle it? I think it would be worthwhile to try and clean it out... but how will you know if cleaning it out 'fixed' it without putting it back in? I know that I myself would have it apart in a heartbeat to figure out how it works and why it failed! I believe one is double-check plus intermediate atmospheric vent (ergo, 3 checks), while the BBFP is only intermediate atmospheric vent (two checks with a vent between them). IRC requires intermediate atmospheric vent, while most municipal water supplies require double check. If you install the more expensive 9D, you have both. That is, at least, how it was explained to me. Take it for what it's worth.

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