old hot water heating system, replaced the circ. pump but had to drain all the water out of the system 1st. as there were no shut-off valves before or after the pump/boiler. System was then refilled & set in operation but at a reduced boiler thermostat temp until I satisfy myself that the air/gas charge in the 1970's era expansion tank was not compromised via the draining down or has been depleted over the 41+ yrs. of operation. I'm sure this type tank has no bladder inside & hence separation between water & air/gas charge like tanks available today. Can anyone offer advice whether the system is still safe with the 1970's era tank - don't want to replace unless absolutely necessary.
Thanks in advance for any advice given.
From Larry
How many gallons is it? Are there any leaks in the tank (rust)? How much are you spending in energy with the 70's system? You may want to look into purchasing a newer one. After you add up energy, repairs and time spent fixing, it may be more cost effective in the long run. You can buy a new one for between $300-$7000. But I have to add you should also look into the tankless systems. My ...»
Ideally this type of tank requires yearly draining for it to maintain its air charge. As time goes on the air is absorbed into the system and gradually fills with water as this happens. Over time you will know wen this is required to be drained out by the temperature and pressure gauge.
When the boiler is cold the pressure should read no more then 12 lbs. AS it begins to heat up ...»
The primary reason why these tanks are changed out is people do not want to drain this tank and service it. Its a matter of not wanting to be bothered servicing it rather then operational.
The tank if its was properly installed should have a red colored valve where the water pipe enters. Attached to this valve should be a little tube shaped object sort of like what a automobile break drain looks like if you know cars. When this valve is turned it allows air to enter into the tank.
The process is the water shut off valve to the tank is turned off. On the other end of the tank is a hose bib in which you would connect a drain line into a bucket, sink or sump pump pit. You turn on the water drain valve then turn on the little vent fitting at other end. This allows air to enter into the tank while the water drains out. Once all the water is gone, turn off the vent fitting and then the drain valve. Once off you then turn on the valve that isolates the tank from the boiler. Some water will fill this tank unit pressure is reached based on the pressure and fill valve on the boiler.
I found Woodbridge Environmental explanation/comments Great & will apply. Didn't see any little tube shaped object at the valve that isolates tank from boiler but will look harder for. Tank has the hose bibb valve to drain - can I use this for the air entry once water has drained, obviously ...»
The device that is connected to the other end of the tank should be located where the water to the boiler pipe is. if its just piped directly into the tank, and some are, you need to find the ...»
So not knowing your exact method of how it was piped, What ever method you can use the better to get air in and water out.
The whole idea of the fill/venting device which is called an airtrol fitting in some parts of the country. Is it allows air to enter tank while draining by not effecting the pressure of the rest of the system. In essence it allows you to isolate the tank from the rest of the boiler system so you do not have to lower the pressure of the boiler and its piping, while allowing you to drain and allow air to enter.
In any case, if there is any way you can get air to enter into the tank while not tapping into the rest of the boiler system you would be better off. As any time you open up the complete system you end up with air into areas where you do not want it.
Your on the right track however, i think you understand know what is going on and what you need to do.
Appreciate all your feedback.