84 Unit Building, and having issues with Hot Water....help is needed.

ALNY

I am the super in a 84 unit building here in Brooklyn, NY.
Last year, the heating company switched out the old B&G 100 with a Taco-007 on the hot water
recirculation line near the boiler.
Everything has been fine in the building until two weeks ago. I have certain units waiting 20 minutes for hot water.
In my building the hot water is fed from the top of the building going down branching through different lines.
The return lines gather, they go to a recirculating pump, and pumped back through mixing valve and back through the building.
I called both building techs.

The heating company says the pump is working, and pressure is fine, most likely someone installed a washing machine causing the imbalance or a center stop faucet.

The building plumber is saying there is not enough pull on the return lines, and suggested B&G 100.
He says this based on the fact that when he opened a drain cock on one of the return lines, the line got very hot very fast....
but the pipe was getting hot as water was coming from return side, going out the drain cock and not from the top of the line like it should have and then going to the boiler.

Any ideas here would be great, or if you have any questions. let me know.

Larry Weingarten

Hi: I think I'd use an IR thermometer to see which returns are cooler than the rest and from there track down any possible cross connections or for balancing the system. Once the return temps are balanced, you can look at the overall temperature drop and if it's too much, look at a bigger pump.

Yours, Larry

RobG

Could you have a bad check valve? This stuff is hard to diagnose without being there. Can you post some pictures?

icesailor

You really need a company with someone who really understands these DHW recirc systems. If you hadn't said that they replaced a B&G Series 100 with a Taco 007 (both cast iron circulators) I would have thought a cross connection somewhere in the building. With 84 units, the odds are good. It can be as simple as a hand shower on a shower only valve with a positive shut-off on the hand shower, and both hot and cold shower valves are open when not being used.

But if those cast iron circulators are used on Potable Hot Water, they can rust up and stop working. 007's can stop working. They need to be brass or stainless steel circulators.

If you ask the tenants, they will swear up and down that they haven't done anything like that. Especially the ones that won't let you in their units. And when you finally get in and find the problem, they give you a big argument that what they did isn't the cause of the problem.

It really is a science.

jonny88

Ive never seen anything but a bronze pump on a domestic recirc line.Could be a few issues as stated above,bad check valves etc,we once had a defective shower cartridge causing fluctuations on hot water .I would check for washing machine or condition of check valves,why not give a shout to JohnNY.

SWEI

What size is the recirc main? A Series 100 is a low head, relatively high flow pump and I'm still trying to come up with an insulated piping layout where it would be the optimum choice.

icesailor

Something to watch for in your application. Multiple recirc returns to the main recirc circulator. If any of those individual recirc lines get air bound, the hot water lays dead in the line and it is a perfect medium for legionella to grow in.

You need to know the building. You need to know if there are places to shut off working recirc's so you can power purge back at the return circulator. If circuits aren't flowing, and you purge into a white 5 gallon bucket, you'll puke when you see the water. And the astringency of the copper sulfate will burn the inside of your nose and sinus's.

Any time anyone gets into a recirc or hot water system, you need to purge it and be sure it is running properly. If you have a Cast Iron B&G Series 100 circulator in place, it isn't running properly.

IME

Post a photo of the offending circulator please.

ALNY

I will post pictures, but here is what i have thus far.
On the return line for each apartment line, i have done the following. On the problematic lines returning to the basement, i turned off the valve line heading back to the re-circulator pump. This way the system can only be fed from the top down like it is supposed to. I was able to get a lot of air in the system from the hot water side, and eventually it stopped bubbling, and the water ran very hot as it was being fed from the boiler. I will be checking if the situation is better.
There are washing machine hookups through faucets than can cause this problem.
As mentioned i looked into shower valves that have turn-offs.
I am also checking to see if any plumbing done without permission.

The return line is 1.5". I will be posting a picture of the setup.

This is a six story building. So should i make a recommendation to management to get a better pump? The plumber also mentioned that we needed to get a pump with a brass body. If so what type would you recommend?

I will post a picture of the setup and some of the returns.

JohnNY

1.5" is huge for a recirc line and a 007 is often no match for the amount of flow per minute a line that size might require to be effective.

I'm no fan of the Series 100, but it's all a guess from here what the right pump specs are.

I will say that I've seen a lot of problems with air collecting in recirculation lines and I always have my guys install a purge setup when configuring for or replacing a pump.

It's a small cost for a lot of benefit later on.

icesailor

I had a similar application and problems. I replaced a brass Series 100 B&G with a Taco 011 or 013 Bronze Pump. I can't figure out how to get to the correct pump on the Taco web site. I wanted a high head, high volume pump.

IMO, the bubbles can form where there is turbulence and low flow. The trick is to keep the water flowing at a high enough volume to keep the water moving, but not so fast as to allow air bubbles to form from turbulence.

Whomever put the cast iron circulators in, I won't comment on. Other than to say he isn't licensed and should only be allowed to watch.

Clothes Washing Machines aren't a problem. As long as the both hoses are connected correctly to the machine. The closed solenoids stop any cross connections. Where you CAN run into problems is that they might still sell single solenoid washing machines. They are the cheapest of the cheap. You have to connect them with a "WYE" hose connection and to use, you shut off one or the other to get the proper temperature. Both if you want warm. If the boiler drain hose connections are both left open, you have a cross connection between the hot and cold. Alive when the machine isn't filling. Another thing that is harder to spot and not common is the really desperate and cheap, who have a washing machine that has a hot or cold solenoid coil fail. The owner can't afford a service call and parts, and figures out that if they connect a wye connector to the working side of the solenoid, the machine will then work. Leaving the building with another cross connection.

You said that all of the units had some form of access to the hot water recirculation but some were cold and you shut them off. If that is so, those cold units are the sources of your problems.

What is the temperature of the hot water being circulated to the units? Does it go through a thermostatic mixer? What is the system temperature being recirculated to the units?

ALNY

Problem was building water pressure was reduced when Backflow preventer was installed. Building pressure was 60-75 from city, and then dropped 15-20 pounds causing uneven pressure throughout. Ever since water pump has been installed, we get 40psi on top (6th floor) and 70-75 on 1st floor. Everything back to normal.