9D-M3 Backflow seeping last season

jlag

Last season had about 1 to 2 gallons of seepage throughout the season from a 9D-MF backflow valve on a Burnham V75 w/ Beckett AFG fitted with a 0.85 80A nozzle heating FHW @ 15 PSI. The pressure was always stable at 15 PSI. Going to change S1156F and 9D-M3 but wondering if expansion tank should be changed as well and if this could have been the root problem. Checked the tank cold and it had 10 PSI in it but I did get a tiny squirt of water out when it first released, but then expelled dry air after that for a considerable time while I released pressure to about 5 PSI.
Question: Is a little squirt a sign of a failure of the expansion tank or could that just be some condensation on the dry side on a 5 year old tank?

HVACNUT

The expansion tank pressure needs to be checked while it's off the system piping. If the PRV is set to 15 psi, then the tank should be pressurized to 15 psi.

Intplm.

There can also be some debris caught in the BFP not allowing it to seat properly. There could also be minor damage at the seat allowing water to pass and leak at the discharge. And what @HVACNUT said.

Be sure to flush/clear the line before installing the new one.

hot_rod

They can squirt, drip, spray intermittently , caused by any fast acting valve in the piping. A solenoid on a dishwasher, outside sprinkler, flushvalves, any device that quickly shuts off creates a shock wave that will open the valve for a second or two.

A swing check upstream can help, or water hammer arrestors at the valves, like wash machine, etc.

If it drips all the time, it has some crud in the seat. They are easy to disassembled and clean.

jlag

Thanks HVAC nut and Intplm.
Bob hot rod, There are big hammer arrestors on the hot and cold at the clothes washer about 10 pipe feet away. It seems to be more of a continuous seep than an intermittent surge. That may make a difference as to whether it's shock related?

HVACNUT

If it's a constant weep then there's crud. I'd just replace it instead of a repair because I'm lazy. Keep in mind the domestic expansion (arrestors) must be pressurized to match street pressure. I would remove and check them as well.
@hot_rod , I like the swing check idea. TOTT!

jlag

I have had a Watts 63190 BBFP on the shelf for a while and never used it. Can I substitute this for a 9D-M3? Someone told me they are the same but I never bought that.
Would anyone know the difference between these two devices?

jlag

Found document links for BBFP and 9D-M3:
http://media.wattswater.com/ES-BBFP.pdf
http://media.wattswater.com/ES-9DM3_M2.pdf

Intplm.

yes

Intplm.

@jlag You can use it. The info you provide above answers your question.

jlag

Changed the BFP today:

There's yer problem.
That is the fill from the street into the BFP.
I also had a zone valve that was leaking internally that I wanted to clean and swap the guts on so I had to do a drain and fill of the system. So while it was open I changed the 25 YO circulator, 15 YO 1156, expansion tank, hy-vent and boiler relief valve.
Back-flushed, filled/bled and fired up. Now, for some reason, the pressure climbs over 20 PSI while coming up to temp. Mind you this system ran at 14/15 PSI hot/cold, night/day, rain/shine before this.
I then dropped the pressure to 5, backed off the 1156 to minimum and opened the feed. It filled to 12 PSI. Boiler temp was about 80F. Fired up to temp and pressure still climbed to 20+ during heating. I actually got scared once on the way up to temp and let some pressure off it. All I can suspect at this point is the new expansion tank. I did verify it's pressure before install with a very accurate digital pressure gauge and it was at 12 PSI. Maybe the bladder needs to "wear in" lol. It is nice and hollow sounding on the bottom and solid on the top (as was the old one). Now there is still a little air in the system, but I can only think the situation will worsen once it is fully bled and there is no air to compress.
Looks like a preventative maintenance shot in the foot right now.
Any thoughts appreciated.
**** UPDATE ****
A day later and the system seems to be running nice now. Maybe the expansion diaphragms are a little stiff when new? Who knows. Anyways, running 12-14 now cold to hot, happy and no leaks. Now if I could just decide on whether to leave the street fill open or closed after the air is out . I have always ran open, but now thinking that a roasted boiler may be better than a flooded basement (many opinions and scenarios that have been discussed). This is pre LWCO code and I don't have one. LWCO may be next move.
What if you ran with the fill valve closed and just had a low pressure cutoff opposed to a LWCO?

jlag

Thanks for your help @HVACNUT, @hot_rod and @Intplm. , you all called it on the crud in the BFP.