130 psi compressor for winterizing?

[Beau_Bo]

Hi - looking at at a Viair 400p compressor to carry al0ng for airing up tires, etc. It is capable of putting out 130 psi and 2.3cfm which is desirable for filling up the truck tires. Another use I am looking at for it is to blow down my camper water lines for winterization. I would approach this cautiously with several faucets open before turning on the air, just wondering if even with faucets open this might be too great a volume/psi input and it might over pressurize my water system. Thoughts?

[B_O__Plenty]

Why can't you blow air through your water pressure regulator using that to keep the pressure down to a reasonable level? I don't know if a Viair has enough volume but I would like to find out..

B.O.

[joshuajim]

joshuajim wrote:
2.3 CFM equates to about 17 GPM. Even with all faucets open that might result in an excessive pressure build up.

OK, let's open up the fluid dynamics books which have been rotting since 1968!

Assumptions:
Water pressure = 40 PSI
Typical orafice size in faucet =1/8"
Resultant flow per formula = 2 GPM +/-

Air pressure = 120 PSI
Same orafice
Resultant flow per formula = 25 CFM

Ignoring line losses, it would appear that as long as one faucet remains open, 2.3 CFM will not overpressure the system.

[CJW8]

I have been blowing out my lines for years using whatever compressor I have and setting the regulator at about 40 PSI. I use a male garden hose to schrader valve fitting and a clip on air chuck, connected to the city water inlet. Someone just pointed out to me this doesn't clear the line between the pump and the tank. I do drain the freshwater tank and then run the pump until it is dry. I think this good enough as I have never had a problem.

[rhagfo]

DrewE wrote:
The simplest and best solution in my opinion is to get an air pressure regulator for use when winterizing. Harbor Freight (among other many places) sells small ones that would be perfectly sufficient for this use for a few dollars. You don't need anything too precise or consistent for this use.

Always leaving a tap or valve open should prevent any great pressure buildup in the plumbing lines. They theoretically ought to be able to withstand 130 psi, though any slugs of water that are being blown along could produce much higher stresses due to their inertia when they hit constrictions etc.

X2!

I have on board air for the Pacbrake, and quick connects and 1-1/2 gal tank. Set the regulator at 80 psi, and have at it.

[myredracer]

My 120 volt Porter-Cable pancake compressor is rated at 2.8 cfm. I've successfully used it for winterizing in the past (no anti-freeze). A Viair at 2.3 cfm isn't much less and might just be fine. RVs are supposed to be tested to 100 psi, but I don't think I'd want to have the piping system pressurized to 150 psi very long, if at all. Get an ordinary regulator with gauge and add quick connect fittings. Note that the Viair hoses have a female fitting on the end, not the usual male fitting.

If you haven't got the Viair yet, get an automatic model otherwise it will run continuous. These compressors have a duty cycle which you should be aware of. Not sure what the automatic models cutoff pressure is. Maybe you could order one with a 105 psi cutoff switch or change it out yourself. Don't bother with the RV version, I think it has additional accessories that you don't really need. Their tire inflator is cheap junk.

I have a Viair 300P that has the same cfm/psi as the 400P, but I modified it and installed a Viair pressure switch that cuts out at 105 psi. When filling tires the psi drops quite a bit when air is flowing.

I'd be interested in knowing if a Viair works for winterizing. Unless you expect to be winterizing where there is no 120 volt power, I'd just get an ordinary portable 120 volt compressor ($100 or less) as Vair compressors aren't cheap.

[westend]

joshuajim wrote:
2.3 CFM equates to about 17 GPM. Even with all faucets open that might result in an excessive pressure build up.

Jim, that's doubtful.

With many 1/2" supply lines venting, I'd doubt there is a pressure rise at all unless using a very large compressor. My 4 cfm, 125 psi Hitachi would never cycle with the situation described.

Even so, I'm thinking that having a pressure regulator in line should prevent over pressure in the system, correct?

Yes, correct!

[Beau_Bo]

joshuajim wrote:
2.3 CFM equates to about 17 GPM. Even with all faucets open that might result in an excessive pressure build up.

Thanks,that was my fear that drove me write the post. Even so, I'm thinking that having a pressure regulator in line should prevent over pressure in the system, correct?

[joshuajim]

2.3 CFM equates to about 17 GPM. Even with all faucets open that might result in an excessive pressure build up.

[Cydog15]

Volume is your friend. Same with a pressure washer. It does more work.

[hammick]

Don't forget to blow out the low water drains as well and also the hot water heater.

[westend]

Boon Docker wrote:

westend wrote:
If you have PEX pipe in the RV and you don't have a cheap filter canister, you should be OK with the little Vlair.

FWIW I have the older air pump system and the fresh water tank is pressurized to push water rather than a pump drawing from the tank. There is a Schrader valve on the fill cap on the exterior. There is also a pressure gauge in this cap. I start my construction grade Hitachi and pressure the tank and system. My pex supply lines are all new, BTW.

I start at the furthest fixture, the bathroom sink, and open that valve. I only have the toilet, shower, and the Kitchen sink after this. Last time, I shuffled back outside to the fill cap and it read 90 psi. That was unexpected but it was a good test for my new plumbing.

You need volume to blow out water lines properly, you have the volume with your system. There is no volume with the compressor the OP is asking about.

Agreed.
He may be able to get the job done with what he has since the whole system doesn't have that much volume. A compressor with a tank is a better solution.

[Boon_Docker]

Beau Bo wrote:

wa8yxm wrote:
Do what I do.. use a pressure regulator between Compressor and RV. I set mine to 50-55 PSI for blow outs. Remove it from the line for inflation of tires.

This sounds like the way I may go with it. Even in the event all the faucets get closed the regulator should limit the pressure increase.

If you are going to use the Viair 400p to blow out the lines be sure to put RV antifreeze in the lines after.

[Beau_Bo]

wa8yxm wrote:
Do what I do.. use a pressure regulator between Compressor and RV. I set mine to 50-55 PSI for blow outs. Remove it from the line for inflation of tires.

This sounds like the way I may go with it. Even in the event all the faucets get closed the regulator should limit the pressure increase.

[Beau_Bo]

FWIW regarding the issue of volume with the Viair. I have a truck camper so the volume of piping isn't near that of a larger RV. Earlier this year I easily blew down the lines with a smaller 12v portable tankless so I'm pretty confident the Viair is up to the task. My question was more directed at the possibility of over pressurization