New Liquidator Install and Pressure Side Low Flow issue

[glewis29]

Hey all, I just got a liquidator after switching over to liquid chlorine, being tired of burning holes in my pool covers and, and wanting to be able to avoid daily maintenance.

Here is a picture of my installation.



It is 1 1/2" pipe into the 1HP/.5HP dual speed pump. It's on a flip switch, so it runs either 1 or .5 HP. Everything after the filter is 2" to increase flow before going back to 1.5" at the Y split for pool and spa.

After hooking up things as shown, I get a flow rate of 5 with the pump on either low or high as long as the OUT float valve is wide open. The problem I'm having is that with the check valve in place on Low I get no water coming into the Liquidator. I think the low back pressure in the pressure side piping is making it so I can't exceed the cracking pressure of the check valve that comes with the 3/8" upgrade kit. I tried removing the pressure side check valve using some spare tubing from the install and the LQ then settles at a flow rate of 2, but if I turn it off, all of the water flows back and I lose prime in my system, so that won't work.

I'm looking for ideas on how I might be able to get the LQ running on low, it runs fine on high. My thoughts are a) try to get a check valve with a lower cracking pressure like this on that says it's only .3psi http://www.usplastic.com/catalog/item.aspx?itemid=26421&catid=489 (although the mfg is John Guest and so is the one that comes with the 3/8" kit and they look almost the same... is it the same?) b) move the point where I tap into the pressure line to a higher point, so that the tubing is all horizontal and maybe there's less pressure from the water in the liquidator (I have no idea if this would work) or c) replumb my pressure side with 1 1/2 inch pipe to reduce flow, and raise pressure enough to open the check valve (this would probably work, but man, what a PITA).

For now I'm just running my pump on high for a couple hours a day, to get the chlorine balance right. Trying to see if I can get this working on low without having to go get a programmable variable speed pump. Another option might be a timer that can control the manual 2 speed pump.

Any help is greatly appreciated.

Thanks.

Greg

 

[Bama Rambler]

Welcome to TFP.

What does your filter pressure run when the pump is on low?

Is inlet of the LQ plumbed on the outlet or inlet side of the heater?

 

[glewis29]

Thanks for chiming in Dave.

Because of the 2" plumbing after the filter, the pressure is very low, like 2-3 PSI. On high it only is at 7 PSI if I'm running my pool cleaner and both spa and pool outlets are open on a clean filter.

The pressure side LQ tap is after the filter, before the heater.

As a side note, I talked to my brother who is a civil engineer specializing in hydraulics and he thinks the biggest problem I have is the 2" pipe. The greater cross-sectional area will increase volume and thus lower velocity and energy provided to the check valve. He said I can likely just take a section of the 2" and make it 1.5" like the suction side and it'll solve the problem. He thinks I don't have to replumb all of the 2" pipe, maybe just the section between the filter and heater, so I might just try that... it's a pretty easy fix.

Thanks.

 

[Bama Rambler]

There are a couple of things you can do to increase the head and get it flowing.

You could install a section of smaller piping like you're thinking, but;
You could just add a valve with the ball or gate drilled out in the closed position so that if you wanted to have more flow you could just "open" the valve and have full flow through the 2" plumbing.
Or you could install a union and insert an orifice plate with a smaller bore to increase the head. That way you could remove it if you ever wanted to.

 

[glewis29]

Good thoughts.

Btw, I got in touch with PST who sells the 3/8" upgrade kit and Bruce was extremely helpful in trying to get me up and running successfully. He was able to provide the technical specs of the check valve they use as well as some other tips. The link to his item on the John Guest site has the same part number as US Plastics (3/8SCV) and shows .02 Bar, which is .29 PSI. It looks like it's exactly the same, so I don't think there's a better option there.

Thanks for the suggestions. I'm going to go over them with my brother and pick one. Which ever direction I pick, I'll install threaded fittings so I can swap it all out fairly easily.

So far, my first summer of getting away from chlorine pucks and getting my pool properly balanced has been very rewarding.

 

[glewis29]

Well, just for completeness, I wanted to come back and post that I finally got my liquidator to work well on low flow (filter pressure of about 2-3 psi). The main things I had to do was to use the 3/8 line upgrade as described by Rabbit in this post http://www.troublefreepool.com/thre...n-(How-to-increase-flow)?highlight=liquidator (Thanks Rabbit!), I also dropped my liquidator into the ground so that the water level wasn't as high and didn't require as much head. Dropping it this much didn't cause any problems with suction side flow. Hope this helps someone. Here are two pictures that show the final setup.

 

[zethacat]

I think burying it was a great idea, and will definitely help with chlorine loss due to sunlight hitting the unit. When cleaning, you'll probably have to siphon the water out of it first since lifting it out of the ground while it is full of water might be difficult.

 

[glewis29]

Yeah, that is definitely the downside. I figured I'd cross that bridge when I got to it. I never shutdown my pool, so I'll just have to see how dirty it gets. Hopefully with borates, the white stuff will be kept to a minimum.

 

[laprjns]

The problem I'm having is that with the check valve in place on Low I get no water coming into the Liquidator. I think the low back pressure in the pressure side piping is making it so I can't exceed the cracking pressure of the check valve that comes with the 3/8" upgrade kit. I tried removing the pressure side check valve using some spare tubing from the install and the LQ then settles at a flow rate of 2, but if I turn it off, all of the water flows back and I lose prime in my system, so that won't work.

I know I am a little late on this but on page 12 of the Liquidator Manual, the trouble shooting guide for "Chlorinator not filling" suggest that its ok to connect the input line between the pump and filter if the pressure is insufficient to keep the Liquidator filled.