Backflow despite check valves

philsego

Hi - I have a 4-zone Weil-Mclain CGA Gold system with Watts-2000 check valves on the feed side, Taco F007-f5 pumps on the return. I'm clearly getting some backflow through the return sides on all zones - despite the Watts-2000's. I was thinking about putting backflow preventers on the return (3/4"), like a Watts LF7, Camco 23407, or Everflow 210T034-NL. I'm partial to the Watts, as I can use this vertical or horizontal. But is this whole thing a mistake? The Watts-2000s are dead horizontal, adjustment screws all the way down (factory setting). Thx!

STEVEusaPA

When you say you are 'clearly getting some backflow'...how far back? Is it just a few feet or is the entire zone heating up?
Before you start cutting pipe, how bout trying some internal flow checks in the pumps.

philsego

From a few feet to through the first baseboard. It's not a huge waste of energy, but it's annoying - and will add up over the coming years. The idea of putting flow checks in the pumps is great, but I can't seem to find anyone who sells just the Taco 007-F5 check valves. In any case, I do have some steel pipe on both sides of the pump for a vertical check valve, and I can cut/solder with no problem if needed.

hot_rod

Is this what you have? These are weighted check type valves. They are not considered a 100% "bubble free" check device and generally do not need to be.

Look for a spring type hydronic check that does provide a tight seal, if you plan on changing them.

I think most pump manufacturers use Neoperyl brand checks, if you know the diameter, they are available.

The checks that we build at Caleffi have that same check mechanism inside that you see in the pump integral checks.

It is getting a bit trickier to spec checks with variable speed pumping. The check needs to be able to "pop" at the lowest speed of the pump, but still have sufficient force to check the fluid. The spring checks have a lower pop pressure, and a better sealing than a metal to metal weighted check.

Keep in mind heat conducts several feet in metallic piping even without flow. are you're it is not just some thermal migration?

Zman

Do you have drawing of the piping setup? Incorrect piping and/or overpumping can cause this.

philsego

Attached is a quick diagram of the system. Note that there are 5 zones (I mistyped 4 zones). The piping is all 1 1/4" before the branches, each zone is 3/4".

philsego

A

nd two photos. I realize that it's too compact to see much.

philsego

In answer to Hot Rod - yes, I have the Watts 2000 check valves, which are the weighted type. Any recommendation as to which brand I should switch to (or add on the pump-side) in order to get a better seal? Thx!

hot_rod

Try turning the screw up and down, maybe the weight is stuck.

It looks like those are used as a 90 configuration, spring checks would need to pipe inline.

Watts and Conbraco have hydronic specific checks in sweat and threaded.

Caleffi checks are also a union, which is sometimes helpful. Low pop pressure and soft quiet seat mechanism. Solder, cool, then install plastic check.

I may be able to build it in a press by press. I think Jomar valve offers a press spring check currently.

Looks like the pumps are pumping into the boiler? Ideally they should pump away from the expansion tank, and the air purger should be close to the boiler outlet?

philsego

I'll follow your excellent tips. The pumps do indeed pump TO the expansion tank. Reconfiguring this looks like a pain - but if you think that's the source of the problems, I'll do this at the end of heating season. In any case, I'll first put in the spring-loaded check valves and see if that solves all my problems. Well... maybe not ALL my problems :-)
Thanks!

Hilly

If you switch brands, some are designed for different or multiple install orientations. That might make your "fix-up" go more smooth.

hot_rod

In some cases you can actually create a sub atmospheric condition in a system by pumping at the expansion tank.

A simple fix might be to remove the pressure relief from the boiler, install a tee there, reinstall the relief and connect the expansion tank at the boiler. I think the entire boiler becomes the PONPC with that change.

The checks leakage may not be related, but air removal and assuring positive pressure in the system would be assured with the correct PONPC.

philsego

This was very helpful. After staring at my configuration for a while, I realized that I can re-pipe the expansion tank without much difficulty - keeping my manifold assembly intact. But that will have to wait until the spring. In the meantime, I'll install the "Bluefin SLCT075" spring loaded check valves. These have very good reviews (at supplyhouse-dot-com), and will fit on the downstream side of the pumps without any problems. I can also do this quickly without delay. Thanks everyone - I'me truly indebted to you for your patience, expertise, and advice.

philsego

Just checking before I start work on this. I'm moving the expansion tank to the upstream side of the pumps (and the entire loop), putting in spring loaded check valves on the output side of the pumps (or should it be on the other side?). Below is the before and after diagram. Thanks again for everyone's help!

hot_rod

Correct, always avoid flow restricting devices on the inlet side of the circulator.
Downstream of the circ 6" or so is ideal to keep the check away from real turbulent flow conditions.

Expansion tank is good at that location, no air elimination device there, keep the Spirovent at the hottest point in the system as shown.

rick in Alaska

Is the flow direction correct in those drawings? Looks as if the supply is coming out the bottom of the boiler. It has been a while since I have seen one of those, so not sure.
Rick

philsego

Hi Rick - Yes - the supply is coming from the bottom of the boiler. I can change that pretty easily when I make the other changes.

philsego

And thanks Bob - I'll be installing the flow checks this Wednesday and moving the tank (as well as fixing one small leak). I can make other changes if need be. -- Phil

philsego

A quick thanks to everyone who advised me on my system's repairs. After making all the changes (and fixing a leak), it's now quiet, efficient, and has an excellent duty cycle. I wound up buying the parts at supplyhouse.com, Home Depot, and one last bit at Metropolitan Pipe in Cambridge MA. Installing everything was a piece of cake once I knew what needed to be done. Have a very happy holiday! -- Phil

Hilly

Photos?? I love post op photos.