11 units of apartments -- cold feed flowing through two 100 gallon tanks in 1" copper?

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I'm reactivating a 1980's era solar thermal system that's been out of service for about 15-20 years.
It's all working now, but I have a concern.

The potable water solar loop has two 100 gallon tanks. The tank hot goes via 1" pipe to meet the 2" cold feed to the 120 gallon commercial gas water heater. My concern is that if I isolate the water heater from cold, all 11 units of the apartment share the same 1" pipe through the solar system.
If I don't isolate the 2" cold feed then not much water will flow through the storage tanks.

The 2" main is centered in the photo.
The first 1" vertical pressurizes the storage tanks.
The second insulated 1" is the warm return from the top of the storage tanks:

PXL_20220326_231517249.jpg

fetch

The red ball valve closes the 2" cold feed to the water heater, forcing everything through the storage tanks.

The building has no backflow check valve to the main.
The building has 4 stories and 11 apartments.

Your thoughts?

--------------------------------------
Note: the system died due to biofilm buildup in the Grundfos pump and/or failed Sunspool heat motor.
 

John Gayewski

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I'm reactivating a 1980's era solar thermal system that's been out of service for about 15-20 years.
It's all working now, but I have a concern.

The potable water solar loop has two 100 gallon tanks. The tank hot goes via 1" pipe to meet the 2" cold feed to the 120 gallon commercial gas water heater. My concern is that if I isolate the water heater from cold, all 11 units of the apartment share the same 1" pipe through the solar system.
If I don't isolate the 2" cold feed then not much water will flow through the storage tanks.

The 2" main is centered in the photo.
The first 1" vertical pressurizes the storage tanks.
The second insulated 1" is the warm return from the top of the storage tanks:

View attachment 82281
fetch

The red ball valve closes the 2" cold feed to the water heater, forcing everything through the storage tanks.

The building has no backflow check valve to the main.
The building has 4 stories and 11 apartments.

Your thoughts?

--------------------------------------
Note: the system died due to biofilm buildup in the Grundfos pump and/or failed Sunspool heat motor.
If I were in your position I would get a solar heating text book (a modern one) and copy the model designs. Or go by a manufacturer's design.

Maybe draw a schematic of how your system is set up. I'm not seeing it.
 

fitter30

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Since the building 30-40 years old or older even it it has a softener i like to see a sample of the hot water pipe downstream of the heaters for buildup. A 2" pipe has a area 4 times of a 1" pipe. Even though a 1" pipe may be able flow enough with low flow fixtures without guesstimating all the fitting and valves total lenght of pipe is pressure drop which effects flow. Using the collectors and a preheat tank might be a better way with a coil in a tank.
 

Master Plumber Mark

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That water has just got to be nasty if this has been sitting dormant that long...
Those heaters are extremely old.... I guess you flushed out the whole system
before bringing this dinosaur back to life....???.

this makes me wonder about the condition of the solar panels too.... do they run water
through them or some kind of antifreeze with a heat exchanger??
I assume that you flushed out the panels real well too....

I don think it is wise to expect this system to hold up for long being from the 80s

and it depends on the brand of solar system you are fooling with..... and the region of the
usa that you live in

I would be getting ready to change out those tanks real soon

and may god have mercy on your soul
 
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