Suction side chlorinator using needle valve

Rangeball

Well-known member
May 25, 2007
785
Several years back there was discussion about using a fine needle valve threaded into a container with hose going from it to the drain plug on the suction side of the pump. I think Hayward made the valve that was able to be closed enough to allow adjustment for our use. I bought one, and never got around to putting it into use.

Has there been anyone using this type of set up? Any problems they've encountered? I can't find much with search.

Thanks :)
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
24,165
SouthWest Alabama
I used the Hayward needle valve on the LQ (Liquidator) and it worked very well. The adjustment is fine enough that you can dial it in pretty close. I don't know about hooking it to a tank with undiluted bleach in it, but I suppose it could work.
 

rocketo

Member
Jul 5, 2015
6
West Tennessee
I tried this method for a while. The problem is you cannot easily judge the amount of chlorine being drawn in. "If I close the valve another 1/8 turn, does that mean 0.5 oz less or 0.025 per hr?"
There are just too many variables that effect the outcome, i.e. ambient temp, condition of filter, skimmer accumulation of debris, etc.

I pretty quickly moved to a Stenner pump where I have a constant, which is the rated or actual measured pump output, that I can use to calculate a reasonably close expected outcome. I know from measuring that the pump (10 GPD rated fixed) has an actual output of 1 oz per 53 seconds +\-, slightly higher than the .889 oz per minute rating. Using that constant (I realize the output may decrease as the tube ages) I can use the timer to deliver a fairly precise chlorine amount across as many time periods as I choose.

Right now I have the pump delivering 50oz of chlorine in each of two separate main pump run times. During the past few days with 100 degree heat the minimum FC level has been a constant 5-6 PPM. Just right for the 45 CYA level.
I can easily adjust the chlorine delivered by + or - the length of time the Stenner runs and know I can get an expected result.
 

Rangeball

Well-known member
May 25, 2007
785
Thanks.

Bama, I wasn't aware you were using it with a liquidator. I have the valve, I guess I'll experiment with it.
 

gary300

LifeTime Supporter
Dec 15, 2014
571
Riverside California
I tried this method for a while. The problem is you cannot easily judge the amount of chlorine being drawn in. "If I close the valve another 1/8 turn, does that mean 0.5 oz less or 0.025 per hr?"
There are just too many variables that effect the outcome, i.e. ambient temp, condition of filter, skimmer accumulation of debris, etc.

I pretty quickly moved to a Stenner pump where I have a constant, which is the rated or actual measured pump output, that I can use to calculate a reasonably close expected outcome. I know from measuring that the pump (10 GPD rated fixed) has an actual output of 1 oz per 53 seconds +\-, slightly higher than the .889 oz per minute rating. Using that constant (I realize the output may decrease as the tube ages) I can use the timer to deliver a fairly precise chlorine amount across as many time periods as I choose.

Right now I have the pump delivering 50oz of chlorine in each of two separate main pump run times. During the past few days with 100 degree heat the minimum FC level has been a constant 5-6 PPM. Just right for the 45 CYA level.
I can easily adjust the chlorine delivered by + or - the length of time the Stenner runs and know I can get an expected result.
Exactly why I went with the Stenner, fixed output. Interfaced to my Easy Touch with Screen Logic I can adjust the Stenner time from my PC with a couple of mouse clicks.
 

Hayward Pool

LifeTime Supporter
In The Industry
Oct 15, 2014
427
Elizabeth
A stenner pump is the way to go. As to drawing chlorine into the suction side of the pump, I would not do this with any tablet feeder as the pH level will be very low.
 

Rangeball

Well-known member
May 25, 2007
785
Thanks, but to be clear, the system I was talking about was for sodium hypochlorite injection, not pucks or dissolved di-chlor.
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
11,043
Franklin, NC
Thanks, but to be clear, the system I was talking about was for sodium hypochlorite injection, not pucks or dissolved di-chlor.
But even liquid injection will cause a pH reduction at the injection point. While the use of liquid chlorine products is generally a pH neutral process there is a lowering when the liquid is added and it is raised again when the chlorine is "consumed" - thus net neutral.

I would think that suction side additions would cause a lowering on pH in the pump/filter, but how much would take Chem Geek to calculate.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,375
Tucson, AZ
User mas985 (Mark) has a link in his signature to his own DIY Injector setup. Mark also did all the calculations for FC and pH rise and discovered that if you tune it properly, you will be perfectly fine.

Cheers,
Matt
 

Rangeball

Well-known member
May 25, 2007
785
True, but I run my pump 24/7 and my daily injection would only be 60 oz, so a very small dribble that should have a really low impact.

Also, as pointed out, Mark uses a similar set up for acid injection and hasn't noted any low PH problems.

- - - Updated - - -

Thanks. I've been through that thread a million times, even participated in it originally, I think.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,375
Tucson, AZ
Thanks. I've been through that thread a million times, even participated in it originally, I think.
Ooops, sorry, I misunderstood your question :oops:

pH changes due to hypochlorite injection should be minimal. Just to be clear, when sodium hypochlorite is add to water, the reaction produces hydroxyl ions (OH-) and the excess lye in the bleach also contributes hydroxyl's so the initial effect is to slightly raise, not lower, the pH. See chem geek's Pool Water Chemistry Post #3. Given the high flow rate of water into the wet end of the pump, I would imagine the pH rise would be minimal at best. As long as you can ensure adequate shut-off with a needle valve so that there isn't a constant source of hypochlorite when the pump is not running, it should work very well.