Question for "Blow Out the Water Line" gurus

Empty Nest, Soon wrote:

Garyl53 wrote:
What is a recommended compressor tank size to be able to do a reasonable job of bowing out the lines at home? If not 3 gal. or 6 gal. then what? Is there a way to use the FW tank as an expanded pressure tank and then run pump and open valves one at a time? Assume you would need to seal off the FW fill vent tube but are there any other vents to a FW tank?

I have a 7-gallon portable air tank (I've always had a separate compressor) which has worked fine for blowing the lines for 15 years.

I pump it up to 90 or 100 pounds of pressure to start. Since I have first emptied the water heater, I have no cause to worry about over-pressure, because the empty water heater will fill with air, so the pressure in the water system will be half or less of the pressure starting out in the air tank, even if I did not open a faucet before turning on the air.

Wayne

I would not recommend 90 or 100 lbs on the city water line, that is well above normal water line operating pressure even for city water.

Air compresses greatly and over pressurizing water lines with air will create potential safety hazards when a waterline or even water fixture fractures or ruptures.

Use the regulator on the compressor, if you don't have a air regulator buy one and USE IT..

Set the regulator to zero then increase slowly up to 30 lbs and not much more than 40 lbs.. This is the most gentle way to introduce air pressure.

You really don't need the high pressure to do this, but what you need is VOLUME which is rated in CFM.. In air compressors you tend to be rated more CFM at LOWER PRESSURES.. So the lower pressure you set the regulator the more CFM a air compressor will be able to supply..

Using low pressures like 25 lbs to 30 lbs allows very small "pancake" compressors like this one from Harbor Freight to safely empty the lines..



Even though it only can supply 1 CFM at 40 PSI and is often "on sale" for $39 or $49..

It just takes a longer time for the compressor to build up and the motor will run more but you will only be running it 10-30 minutes max..