Correct pressure (<5psi or ~20psi?) and equipment (compressor/shop-vac/leaf blower) for blowing out the lines

baip

Active member
Aug 7, 2019
33
Sunderland, MA
This is my first time winterizing our in-ground pool. I've read many many articles and forum posts on this topic for the fear that I may overlook something and end up damage the equipment or the underground piping. I have a Freeman 1.5 HP / 6 gallon compressor, a 3.5 HP Shop-Vac, and a Sun Joe 155 MPH/200 CFM leaf blower. None is particularly powerful. Some say that a leaf blower may be sufficient, but I couldn't have a good seal when attaching the square-shaped outlet (with the tube already taken out) to the skimmer inlet.

The previous owner left an adapter that attaches to the skimmer inlet and a vacuum hose. However, it looks like the blower side of my Shop-Vac has a small hole just below the hose attachment point. It does not appear to be a defect but some sort of a safety relief hole by design. I guess the plastic body of this particular Shop-Vac model isn't built to withstand pressure. Has anyone using Shop-Vac experienced similar issues?

For now it looks like that our only option is to use the compressor. Even though it may not have enough air volume, there won't be a continuous water volume remaining in the pipe as long as the compressor can build up enough pressure to counteract the depth of the water, which should be good enough for winterization purposes. Many say that we should use 20--25 psi, but the user manual of our Hayward Super Pump has this warning: "Purging the system with compressed air can cause components to explode, with risk of severe injury or death. To avoid, do not purge the system with compressed air. Use only a low pressure (below 5 PSI), high volume blower when air purging the pump, filter, or piping." So for our system, should I just use 5 psi and wait long enough until air comes out of the other end?
 

Texas Splash

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A good person to help you with this question is @Catanzaro. He knows all the tricks for getting those lines winter-ready with a variety of equipment and techniques. Hopefully he'll see this post and give you a shout soon.

Welcome to TFP! :wave:
 

Catanzaro

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Jul 30, 2014
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Monmouth County, New Jersey
Baip:

Your Sun Joe and your shop vacuum will NOT do the trick. The air compressor will do the trick (you can burp the lines) by holding a winter plug, then releasing, then building pressure, then releasing again. Last year, I used a blow-thru plug as an experiment with very little pressure on a shop vac with under 20 PSI (If I remember correctly). The key was to keep the compressor running as it will run out of air pretty quickly.

My concept thread may have the actual test, and I would suggest highly you read this over as you should have more ideas on which way you wish to proceed! There is also the thread about the Blow-thru plug.

You can attempt very low pressure, but keep the compressor running. Highly suggest you purchase the blow-thru plugs are they are a wise investment.


 

baip

Active member
Aug 7, 2019
33
Sunderland, MA
Catanzaro and Pat: Thanks for replying. Holding a plug to build up a pressure is a really good idea to get more water out. I was thinking that even without this, I should be fine (?). My rationale was that if there were a solid column of water inside the pipe, then the water pressure depends only on the depth, and a few psi of pressure should be more than enough to push at 9-feet depth. So after purging, even if the air volume from the compressor can't keep some of the water from flowing back, there would be no continuous section of water and thus no danger of freezing damages. Does this reasoning make sense to you or is it flawed in some way?

On the other hand, I'm curious if there is any basis for the warning of purging at >5 psi pressure. I think I read somewhere that pool plumbing was built to withstand a maximum pressure of 30 psi. Is there any part of the pump-filter-pipe-etc. system that calls for the much reduced air pressure?

I'm going to read the two posts on closing IGP and blow-thru plug, and try it out this weekend.
 

Bama Rambler

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If you look at the pool equipment you'll see that it's rated for at least 50 psi. While I wouldn't put 50 psi on the plumbing, anything 30 psi or less isn't going to hurt anything.

Also ~27" of water = 1 psi. I usually round it to 2' WC = 1 psi for close guestimation. So 9' of water would be about 4½ psi. A little more than a leaf blower or a shop vac will produce pressure wise.
 

Catanzaro

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Jul 30, 2014
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My experience with the air compressor is 20 PSI. The tank will empty quickly, which is not a big deal, but keep the air moving. Also, I would not use the NPT fitting on the pump basket, but more of a blow-thru plug as it takes time to fill the chamber up. You want to only work with the plumbing.
 

baip

Active member
Aug 7, 2019
33
Sunderland, MA
Also ~27" of water = 1 psi. I usually round it to 2' WC = 1 psi for close guestimation. So 9' of water would be about 4½ psi. A little more than a leaf blower or a shop vac will produce pressure wise.
Yes, that's about what I remembered; just did the calculation again and a slightly more precise number is 3.9 psi.

My experience with the air compressor is 20 PSI. The tank will empty quickly, which is not a big deal, but keep the air moving. Also, I would not use the NPT fitting on the pump basket, but more of a blow-thru plug as it takes time to fill the chamber up. You want to only work with the plumbing.
Thanks. I read three of your posts on pool closing (overview, blow-through plug, modified pump cover) -- all very helpful! The only thing I'm still trying to understand is the emphasis on air volume. Unless there are other important factors being neglected, force balance would mean that anything more powerful than 4 psi (in my case) should be able to move water, however slowly. Air volume would be important if we had to build up sufficient pressure in the presence of leak. If there is no leak, with compressors it feels like that keeping a low pressure might actually be beneficial for keeping a plug flow instead of shooting a small hole in the middle. Anyway, I will test it out this weekend, starting from a low pressure and work the way up to 20 psi if needed.
 

Bama Rambler

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You need volume in order to clear the pipe. Think of it this way. Take a straw and put it in a glass of water and blow into it. How long does it take to blow all the water out of the glass?
Now take a hair dryer and blow into the glass. How long does that take to blow the water out of the glass?
The pressure is about the same but volume of air is doing the work.

Once you have enough pressure to overcome the waters head, it's volume of air that displaces all the water.
 

baip

Active member
Aug 7, 2019
33
Sunderland, MA
Once you have enough pressure to overcome the waters head, it's volume of air that displaces all the water.
This is actually my view as well. Both will work; lower air volume just takes slightly longer.

So I successfully blew out all the lines today. The lowest mark above 0 on my compressor's pressure gauge is 10 psi, so it doesn't have the precision to let me start at 5 psi. 10 psi worked and the 6-gallon tank held up a little bit longer. Since I was using a 1/4'' NPT air fitting I already have, the compressor has to fill up the pump basket and all other dead space, and for whatever reason, the pressure reading on the filter is lower than the reading on my compressor. Also I should have thought this, but there is no way I can maintain a plug flow at this pressure and pipe diameter. Water and air comes out together, and certainly a higher air volume would work better in this scenario.

Another tidbit about my experience: my multi-valve is probably leaking since the previous owner installed a ball valve on the waste port. I spent quite some time unable to build up pressure to blow returns before I realize that I had to keep the filter drain plug on along with setting it to recirculate..

Finally (I'm also posting this as a new question), I think I have a Hayward Jet Air III. The fittings were not installed, but I found a few spare parts that look right (SP1434-B, SP1434-D, SP1434-T). I used either a size 11 or 12 rubber plug, which got pushed in a little too deep, and I was unable to get it out. It stopped the air but I fear the difficulty at next year's opening.. What's the correct winterizing plug to use for this return? Is the rubber plug OK or do I need something like this?
 
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Catanzaro

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TFP Guide
Jul 30, 2014
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Monmouth County, New Jersey
Finally (I'm also posting this as a new question), I think I have a Hayward Jet Air III. The fittings were not installed, but I found a few spare parts that look right (SP1434-B, SP1434-D, SP1434-T). I used either a size 11 or 12 rubber plug, which got pushed in a little too deep, and I was unable to get it out. It stopped the air but I fear the difficulty at next year's opening.. What's the correct winterizing plug to use for this return? Is the rubber plug OK or do I need something like this?

Baip:

We closed a friends pool with the same fittings on the return jets (steps in the deep end). The tools removes these fittings and also installs them. The winters plugs # 11 (fit snugly) and without having to over tighten them, and there are no leaks as the front of the housing is flush. Can I ask you why you used the SP1434TP Jet III Test Plug to winterize, or am I missing something?
 

baip

Active member
Aug 7, 2019
33
Sunderland, MA
Baip:

We closed a friends pool with the same fittings on the return jets (steps in the deep end). The tools removes these fittings and also installs them. The winters plugs # 11 (fit snugly) and without having to over tighten them, and there are no leaks as the front of the housing is flush. Can I ask you why you used the SP1434TP Jet III Test Plug to winterize, or am I missing something?

I am actually using a #11 rubber plug, except it went in too deep and I had trouble removing it (to build up pressure and re-plug). So I suspect I did something wrong. I was searching online and found this post and a Q&A here that says SP1434TP was the plug to use for winterization.

I wonder if the people who closed and opened my pool installed the lock ring (SP1434-D) but not the nozzle (SP1434-B). If so, maybe after I removed the lock ring I would have better access to the plug.
 

anthonypool89

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Aug 26, 2016
774
Berks County, PA
The way I always view it is - if there's enough air to push the water out of the lines, that's all you need. Unless I'm mistaken, the water (or most of it) has to empty before air bubbles start to come through. I also have nothing on my compressor between 0 and 10 so am probably somewhere in between there. I've always found that with too much pressure, it's nearly impossible to get the plugs all the way into the angled return lines (especially the 2nd one once the first is plugged).
 
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