"Dead Leg" issues

Florida Penguin

Platinum Supporter
LifeTime Supporter
Mar 23, 2008
I am not sure where this question should go, but this forum seems liked the best fit.

I have a pool/spa combo. The spa has an independent, dedicated 2 hp pump that is only used for the spa jets. The main filter pump returns water to the spa (which overflows into the pool in normal "pool mode." ). The only way for water to flow in the jets for the spa is to turn on the spa jet pump. I don't know exactly how much water is in the piping, but lets say there is about 75-100 feet from the pump to the spa.

So, for the first few months of my pool, I didn't even think of this issue. Then when I had problems with keeping my FC up, I thought about this "dead Leg" of pipe that doesn't get circulation that often. Could I have an alge bloom in this "dead leg" pipe?

So I shocked the pool with the spa jet on for day, then I set my timer to run the spa pump every day for one hour. My theory is to keep fresh water (with chlorine) circulating in the pipes each day.

Any thoughts on this. Is this a good idea, or overkill? :shock:



Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
Absolutely a good idea. My pool first shows signs of algae in any little nook or cranny it can find.

You may not need more than 15 minutes daily but to flush that old water out and replace it with new, chlorinated water is really smart.


Well-known member
Mar 27, 2007
Morris, IL
How about this, if you shove a rag in the other ports, can you get water to come out of that one? Maybe it is just a matter of too many ports on one leg.


LifeTime Supporter
Apr 9, 2008
SC Midlands
I have the same plumbing set up as you Florida Penguin. I have only had algae once and it definitely started in the "dead leg" on the spa booster loop. I could see the algae in the pump basket. I have since been turning on the booster several times a week and have not seen algae since. I have thought about modifying the plumbing to get a constant circulation through that loop, but have yet to do anything. I don't think that is overkill at all. I may just have to install a timer on the booster pump circuit to automate the process.

Florida Penguin

Platinum Supporter
LifeTime Supporter
Mar 23, 2008

Not sure what Sevver is getting at in his reply....

But thanks for the support from the others. I am not sure how much I have to run the spa pump...I might drop the time to 30 min a day rather than one hr, but I think the cost in terms of power and wear on the pump is probably trivial.