Pressure tank winter

[Qwertyjjj]

I have a pressure tank in the garage for irrigation. The pipes will be cleared with an air compressor in autumn.
Some of the fittings are plastic threads or polypipe couplers with barbs.
Is there any danger of water staying in these fittings, freezing during the winter, and splitting the plastic?

Generally do the plastic connectors ever fail?

 

[Craigpump]

Plastic is brittle, so yes if there's water left in it, it will freeze and break

 

[Sponsor]

 

[LLigetfa]

If you can blow the lines out with a sizable compressor and they are properly pitched to drain, I doubt there would be enough water left to fill a section full bore to the point where the freeze expansion would break things. Do keep in mind however that it can be hard to properly pitch poly to drain.

 

[Qwertyjjj]

Plastic is brittle, so yes if there's water left in it, it will freeze and break

The air compressor should sort most of the water. I guess I was wondering about the threads.

 

[Qwertyjjj]

How can I connect an air compressor to a 3/4 polypipe fitting or something on the pressure tank?

 

[LLigetfa]

I plumb in a Tee where I want to put a snifter valve.

 

[Qwertyjjj]

Aren't air fittings a different size to water pipe threads?

 

[Qwertyjjj]

On my pressure tank tee, there's a 1/4" pressure switch and a 1/4 pressure guage.
Possibly the slot where I have a 1/2" faucet / boiler basics I could instead connect a splitter and add the snifter valve with a reducer?

 

[LLigetfa]

I don't know what you mean. A snifter valve is intended to connect to water plumbing and normally uses a 1/8" or 1/4" MPT. If you google for snifter valve you can find them in different MPT sizes.

MPT is the same regardless of whether it is used for air, gas, water, or hydraulic oil. Use the appropriate reducing Tee or reducing bushing. If your pressure gauge is in a suitable location to introduce the air, then you can place a small Tee there. If not, there are many reducing Tees available since it is common to use then to connect pressure gauges and/or switches. Many tank Tees come with extra ports with plugs in them.

Possibly the slot where I have a 1/2" faucet / boiler basics I could instead connect a splitter and add the snifter valve with a reducer?

Assuming the valve can take a garden hose, you could get a 3/4" female hose thread to FPT adapter into which you screw the snifter valve or a male air QC.

 

[Qwertyjjj]

Thanks, I'll see what the store has.
What connector attaches from compressor to snifter?

Also, I need to blow out 3/4 poly X 150'. What size compressor is best? Could be more pipes in future though I guess I could add valves to blow out zone by zone not necessarily needing a bigger compressor.

 

[LLigetfa]

What connector attaches from compressor to snifter?

A tire air chuck, same as you use to put air in a tire.

 

[Qwertyjjj]

Do I use yellow gas ptfe tape or white water ptfe tape on these threads seeing as they come into contact with both?
Or just some pipe dope : covers water and air.

 

[Reach4]

Both would be best. Yellow PTFE tape is perfectly fine with water. It is generally a better grade that your cheaper white tapes.