Question for "Blow Out the Water Line" gurus

Empty Nest, Soon wrote:

Gdetrailer wrote:

. . .

I would still recommend using a regulator even with a portable tank..

This allows you to turn on the air at a slow controlled rate instead of shocking the water system..

Fortunately for myself I can reach my RV via 75ft of air line.. Otherwise I would use my small pancake compressor.. Doing so eliminates the short coming of a small air tank supply.

I understand that I cannot have a sudden "explosion" of high pressure into a line that is full of water. However. . .

1) Turning on the air with the portable tank is necessarily gradual, as it requires about 3 or 4 turns of a little valve in the outlet, and

2) In my case, the water system is pretty much empty because I have already drained the water heater and opened up the low point drains.

If I had more than 50' of air hose, I might use my compressor to do the job. It has a pressure regulator for the output, which I would dial down to an appropriate pressure. I find the portable tank more convenient for me personally.

Not trying to argue, only intended to answer the question of how big a tank folks have found satisfactory for blowing the lines. For me, the 7-gallon tank has been sufficient.

Wayne

Putting potentially 90 PSI SUDDENLY into a system designed for 50-60 psi whether full of water or air is a recipe for disaster.

I am not arguing, I am stating a fact that water does not compress, a sudden addition of a high pressure source and the water /air has no where to go.. Even a 7 gallon air tank can create enough shock at that pressure to break fittings..

Keeping in mind with PEX, ALL the factory connections are made with CRIMPS to the fittings.. Those joints are most likely the weakest part of the system other than the toilet valve..

You are very welcome to continue on with how you do it, it obviously works for you. But I would caution folks that shocking your water system with a quick jolt of high pressure potentially will lead to a premature failure of the weakest part of the water system..

I personally take a gentle approach by use of a regulator which gives precise control over how fast and how much pressure is placed on the system..

You don't need a huge blast of air, only enough air to "push" the water out..