Does length of suction side pipe matter to Liquidator?

Txmat

LifeTime Supporter
Jun 18, 2010
424
San Antonio
I am getting ready to replace my flexible pipe with pvc in anticipation of adding the Liquidator. At present I have an ABG with the skimmer almost directly above the pump. It is a straight drop from the skimmer to the pump of about 3 feet. I remember reading somewhere that the Liquidator works best if there is a longer run from the skimmer to the pump. Is this correct? Should I run the PVC down the side of the pool before doubling back to the pump? I currently have 1.5 inch pipe on the suction and return. I plan on using 2.0 on the suction and 1.5 on the return - is this a good idea?
 

Bama Rambler

Mod Squad
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Jun 22, 2009
23,371
SouthWest Alabama
You're right that suction head makes a difference in how much flow you can get The longer the run of suction piping is, the greater suction head. However a few feet usually won't make much difference. If your skimmer is 2" then you're going to have a very low suction head. The best thing you can do is put plumb a valve just below the skimmer or at least before the connection of the LQ. That will allow you to artifically increase the suction head that the LQ sees and therefore increase the flow through the LQ.

Having said all that, you may not need to increase the suction head in the plumbing to get the LQ to flow enough to satisfy your needs.
 
G

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See, I told you he would answer that with flying colors... Thanks Bama!
 

mas985

TFP Expert
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May 3, 2007
12,531
Pleasanton, CA
Plumbing the liquidator injection point as close to the pump as possible will also increase the suction on that line. The highest suction being at the pump drain plug.

Another trick that introduces less head loss but drops the pressure in the line is a few inches of smaller diameter pipe with the injection point in that section of line. Basically a Venturi.
 

Txmat

LifeTime Supporter
Jun 18, 2010
424
San Antonio
So Mark would you suggest I keep the 1.5 inch suction pipe and if I do not install at the pump drain plug I insert a short section of 1 inch or 3/4 inch pipe before the pump and attach the liquidator there? I had planned on using a 2 inch suction pipe and keeping the 1.5 for the return based on some of my readings of your posts in the Pump/Plumbing section which I may have misunderstood. Thanks for the advice.
 

Bama Rambler

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Jun 22, 2009
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I agree with Mark that a short spool of smaller pipe would work but I would try it first without it because you may not need anything. That's why I suggested the valve. If I were going to install a smaller spool peice I'd install it between two unions so I could install a larger spool if I didn't need the restriction. I will however bow to Mark as he's the hydraulics expert around here.
 

mas985

TFP Expert
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May 3, 2007
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Pleasanton, CA
What I was suggesting isn't really a spool of pipe but a very short (< 6") section of smaller diameter pipe which would simulate a venturi. The injection point would be in the smaller pipe.

The venturi concept relies upon the fact that pressure will drop when water velocity increases. So by downsizing the pipe for a short section, you will get a pressure drop (more suction) but it is temporary unlike head loss with a valve is. The pressure rises once again once the pipe expands back to the original size.

For example, if you had a step down from 2" to 1 1/4" pipe at 50 GPM, the pressure drops by 1 PSI just due to the velocity change and other 0.15 PSI due to the transition and pipe. The total head loss induced by the step down, 6" of pipe and step up is less than 0.9' of head. To get a 1.15 PSI drop with a valve, you need the equivalent of 65' of 2" pipe with a head loss of 2.6'. So all of the pressure drop with valve comes as head loss while most of the pressure drop in the venturi simply comes from the pipe reduction and head loss is kept at a minimum. The larger the step, the bigger the pressure drop.

But I agree, it may work fine without that but it depends on what the Liquidator actually needs in terms of suction. But given the issue with the Liquidator and the fact that there is less than 0.5' of head loss difference between 5' of 2" and 1.5" pipe, I wouldn't bother with 2" pipe. It may end up causing more problems than what it is worth. I would keep the pipe you have and just see if works. If not, then we can discuss other options.
 

Txmat

LifeTime Supporter
Jun 18, 2010
424
San Antonio
Thanks Mark and Dave. I will follow Mark's advice. Since I have the flexable pipe and the liquidator calls for PVC and since I want to add another return and some valves I plan to re-plumb the whole system. I will do it with 1.5 inch pipe and then if the liquidator needs it I will add the short 6" smaller pipe. In light of the heat here in Texas I will probably put this off for another month. I just loss a friend who had a heat stroke and this has made me keenly aware of keeping my outside work to a minimum as long as we are having 105 heat index days. I will report on what I do and let everyone know how it works out.
 

Dougschw

Member
Nov 2, 2015
6
Milwaukee, WI
Hi All,

First post on this site. I just installed a liquidator last week. I keep my Pentair intelliflow at 1500 RPMs and run it 24/7. This is enough pressure to keep my heater going and my UV lamp on. I do this to maintain a steady pool temperature of 90F on my indoor pool. Since I installed the liquidator, I have not been able to keep my pump filter basket full of water. It will stay about half full at 1500 RPM. Thus, I am pulling air through my system and it is noisy and I have air bubbles coming through my returns. I have about 10 feet of hose going to and 10 feet of hose coming from the liquidator just so keep the hoses out of the way by running them below my heater and around some other plumbing. I could shorten this hose and go directly across the floor of my equipment room.

Will this help to get the suction back up? Or, are there other tricks to get the suction back up?

Any suggestion to improve my suction side.