HW recirculation problem

[toddo]

Greetings,

DIY plumber here. I hooked up a passive thermosiphoning system yesterday. Almost works, now I have instant "warm" water, then cool, then finally hot. Close but no cigar.

Any suggestions for tweaking greatly appreciated.

Details...about 50' run to most distant fixture. Supply is 3/4 main with 1/2 to fixtures. Return loop is 1/2. Tied into bottom of electric water heater located in basement.

Per something I read, I tipped the swing check valve into a slightly open position when installing. Is that the problem? In researching the project, another "authority" suggested drilling an 1/8 hole in the valve flap with no mention of tilting the valve open. Other sources don't mention any special treatment of the scv.

Have most of the supply and return insulated but not all. Can't believe that's the problem. Plan in leaving the last 15 feet or so of the return uninsulated.

TIA for any thoughts,
Todd

 

[toddo]

Correction, tried to take a shower. Brrr - Warm only, never got hot enough. The return loop has to be running backwards, right? Shut the loop off for now.

Might be a hack plumber but at least I am smelling okay now.

Toddo

 

[Sponsor]

 

[hj]

system

Without seeing the entire piping system, we do not even know if it is set up so that a passive system would work. If shutting off the loop restores hot water then that is the problem, but unless the check valve is tipped so far that the reverse flow cannot close it, that should not be the reason.

 

[Toolaholic]

suggestion

you want instant hot water at a distant shower 0 dark thirty?

put in a recir pump with timer. mine runs 5 am-7am 5 pm 9 pm

home comfort series screws on w h and manafold under most distant vanity NO NEW LOOP PLUMBING under $300 i hr work

moma will LOVE you

 

[toddo]

Without seeing the entire piping system, we do not even know if it is set up so that a passive system would work. If shutting off the loop restores hot water then that is the problem, but unless the check valve is tipped so far that the reverse flow cannot close it, that should not be the reason.

HJ, I tried to read as much as possible prior to starting. Remember someone stating emphatically about the importance of proper engineering. Bet that's you, huh?

Question if you don't mind. If the valve isn't tipped too far, what else "could" be the problem?

Thanks,
ToddO

 

[toddo]

you want instant hot water at a distant shower 0 dark thirty?

put in a recir pump with timer. mine runs 5 am-7am 5 pm 9 pm

home comfort series screws on w h and manafold under most distant vanity NO NEW LOOP PLUMBING under $300 i hr work

moma will LOVE you

Tool, if I can't solve this that's probably my next move. Downside is that I (we) work out of my home, ideally the timer would be set something like 6:00 a.m. to 9:30 p.m. Thanks for the suggestion.

ToddO

 

[hj]

loop

As long as you have the return pipe, you do not want, or need, the Grundfos Comfort system. From what you have descsribed, there is no other cause of the problem, assuming you really cure the symptoms by shutting off the valve at the heater.

 

[Breplum]

I have read in more than one place about drilling an 1/8" hole in the check valve on pumped systems. I also have literature written by an engineer who says to drill an 1/8" hole in a gate valve to reduce flow in pumped systems.


Is there enough flow in a thermosyphon to even have a check valve? I kind of doubt it. How about trying the system w/o the check valve.

My opinion after owning a Laing undersink 'one pipe' recirc pump system with thermostatic switch and timer (and added air switch for more control). They are ok, but a water waster when you want cold water again, because you have to dump hot water from the cold line after the pump has run.

 

[hj]

check valve

Without the check valve the return line will be a direct path for cool/cold water from the water heater to the far end of the system. Since it would be "direct" it will have less restriction than the normal route so you would have a better chance of receiving cold water there than warm water. You should not use a gate valve with the pump if you intend to "throttle" the flow. You would use a globe/compression/balancing valve, and it would be between the pump and the connection to the tank.

 

[Breplum]

I know we got off the thermosyphon track but wanted to share this Re: pumped systems and erosion in pipe, I dug out the article "The Pitfalls of Residential Hot Water Recirculation by Thomas L Liston P.E. from Plumbing Engineer Magizine dated April 2005 where he states " So what I recommend for a residence is that you don't pump more than 2/3 gpm." He then recommends the insertion of a calibrated orfice in the return line...like Bell & Gossett 1/2" Circuit Setter set at about 22degrees. or "A gate valve with a 1/8" hole drilled through it will, when shut, do the same thing."
He also recommends using Type K or L copper, not Type M to prevent premature erosion in recirc systems. And always use a check valve.

I can xerox a copy of this article if anyone wants it.
marcbrenner@hotmail.com