Some Quick help ....re-circ problem public housing

Al Letellier_9

Just thinking out loud without seeing the set up:
Pump velute air bound and cavitating
Cross connection somewhere
Bad pump impellar (burned out or damaged when water lost)

If it worked before the break, ask yourself what's changed..something obviously did. If all the air has been purged out, something failed during the loss of pressure. Find it and your problem is solved

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mark smith

some Quick ideas trouble DHW recirc in public housing

had a customer with a water main break ...
11 story bldg., 10 "risers" drop to the first floor, and service a vertical string of apartments

first the system was Air-Bound..
no hot water at the upper floors,hot water had to come up from below to feed the upper floors, due to air.. lower floor had good hot water ...purged....good DW supply now, Except the last 3 on the top loop "risers" in that system...

those 3, now, have Cold hot water at the bottom, no matter how long you let it run...

the recirc line is warm, that collects these risers, the pumps have been verifyed as running
so, since there is blasting hot water at the top apartments, water has to be coming down from the supply above..

but 7 floors down it's petering out
the recirc line offn these is warm ....

what the hay can be wrong now ...???

Brad White_25

Can you

post a diagram? That might help. My mental picture may not reflect reality....

mark smith

howsabout a better desription

the Supply comes down outta the penthouse, and rings the 10th floor in a horseshoe

there are 10 "riser", they really Drop, that supply a Vertical string of apartments down to the first floor

then, another "horseshoe", or ring,collects the ends, and is hooked to a 1" recirc line that returns 11 floors up to the penthouse mech room

the ones with the problem do have a warm line to the recirc horseshoe ...
they are at the end of one side of the horsshoe..... sooooo

what can be wrong here ..

pumps 'r pumpin'
line is warm

still smells of not enuff recirc

it's worked fine for years ..

mark smith

pumps pulled and verifyed operation

still thinking there's air in the system yet .
the trouble lines are where it cmmonly gets airbound

it's the only answer that makes sense