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In lieu of buying an actual air pump to use just once a year to close a swimming pool before freezing, I'd like to use the blower feature of a wet/dry vac.

I'm trying to choose between a 5HP and a 6HP (both peak) wet/dry vacs. Will the extra 1HP make any difference in the strength of pushing a 10-12ft column of water?

How do I determine the HP needed for a given column of water?

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  • You're planning on emptying the pool, one wet/dry vac load at a time? Could take a while... – Daniel Griscom Jun 25 '16 at 20:53
  • Is there anywhere on the property or street that is lower than the bottom of the pool? – Harper - Reinstate Monica Jun 25 '16 at 22:21
  • Assuming your just blowing out the plumbing, most shop vacs will work. If you Google "pool blower winterize" you'll find most of the "made for that purpose" blowers are 3hp, it doesn't take a lot a pressure surprisingly. I've seen people use gas powered leaf blowers as well. – Tyson Jun 25 '16 at 22:30
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I don't think this is going to work.

Shop-vac posts their specs here: https://www.shopvac.com/specifications/quiet_series.asp

Even their most powerful vacuum only has a sealed pressure of 64 inches. I would presume that the blower would have the same pressure.

I don't know specifically what you are using an air pump for to close a pool but I think you may need to use a compressor or some other device.

Good luck!

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  • Is it established in this context to present pressure by inches, rather than, say, by psi, where a column of water is the implicit reference? – Calaf Jun 26 '16 at 13:15
  • You said you wanted to push a 10 to 12 foot column of water. You didn't specify a desired pressure. Inches of water are used in instrumentation and HVAC a lot. 10 feet of water or 120 inches is ~4.33 psi. Shop-vac one of the more popular brands of utility vacuum only rates their 6.5 HP vacuum at 64 inches. Head is another way to refer to a vertical column of water. A pump could move large volumes with low head or high head and low volume or both. Vacuum sweepers are great for moving a large volume of air but are not designed to create that much pressure. – ArchonOSX Jun 26 '16 at 23:42
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If you use a blower (such as from a wet/dry vacuum, or from a leaf blower), you'll be able to blow the pipes to the skimmer(s) and the return pipes to the pool. You will most likely be unable to blow the pipes going to the intake at the bottom of the pool (if you have one). The 3HP-6.5HP air pump will be insufficient for that water column. You'd be asking too much if you try this with an air pump that is weaker than 3HP.

With a dedicated pool blower, you'll be able to blow all lines.

However, you do not actually need to blow the bottom of the pool. That area never freezes (assuming you're not that close to the North/South pole). If you hire a pool company, they will blow the bottom of the pool as well. It will be quite evident from the turbulence that the air is coming out from the bottom of the pool. Once they're done pushing, the water goes back right through.

The key is to lower the level of the water far enough below the skimmer (you don't want rain/snow water to go back into the skimmer before the frost is gone). Another key point is that you must seal the pipes coming back to the pool. Estimating how far you have to lower the level of the water (you'll have to purchase these tens of thousands of gallons later from your water company) is perhaps the main art in doing this task yourself.

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