Chlorine Build Up Clogging Underground Skimmer Line?

by Mike
(Syracuse, NY)

I have used 3" tri-chlor tabs placed in the skimmer basket for ten years. pool pump is on a timer and runs for 12 hrs/day. late last summer I noticed that the vacuum wasn't performing well. This season it lost all suction.

Turning the valve to 'port 1' (for vacuum) shows a severe lack of flow, no vacuum suction. My local pool guy says that over time the tabs may have created a crystallized build up of something (chlorine?)in the skimmer line underground. He wants to charge me HUGE $$ to break up the concrete pad, dig a new trench and replace the line. I believe there must be an easier way.

Is there a chemical that I can use to fill that line and dissolve the crystalized build-up? It's the same type of build up you would see in an in-line chlorinator after a few seasons of use.

And no, the line is not clogged by debris. I have snaked the line with a plumbers snake and that keeps the water flowing, but not 100%. What can I use to open the line and increase the flow and remove this crystalized ball of chlorine?

Thanks for your help


Thanks for the question Mike

In all my years of pools, since 1999, I've never heard of chlorine tabs crystallizing or clogging up a skimmer. I've told people for years to never put tabs in the skimmer. Always use a tab feeder or a tab floater. I'm not saying this problem has never happened, but I've personally never seen it.

Here are some posts to look over:

How Do I Fix Low Skimmer Suction?

The above post is good to review.

Little To No psi

Sand Filter Pressure Increases And Low Suction

If you do have a clogged line due to chlorine residue, I'm not aware of any chemical that will dissolve it. I would be very hesitant to pour muriatic acid in the skimmer as this can cause damage to the internal parts of the filtration system.

Are you sure it couldn't be high calcium buildup? If it is you might be able to use a product such as BioGuard Scale Inhibitor. If you want to go a more natural route, I've used vinegar to remove tough stain and certain kinds of buildup.

Look over the posts above and try the tips. I've looked online for more information about this particular issue but can't find anything.

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.

Contact Me


Hope this helps and have a great Summer.


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Jul 17, 2014
Chlorine problems
by: Priss

If the chlorine levels in my pool is a burnt orange color what going on. Needed much help.. Thanks

Jul 18, 2014
Problems with Chlorine
by: Robert

This usually indicates the chlorine is much too high. I'd encourage you to get a Taylor K-2006 pool test kit. It's the best on the market and will give you the actual numbers you need.

Chlorine cannot rise on its own. Know the gallons of your pool and the amount of chlorine you need. It's 1 gallon of chlorine per 10k to increase 10ppm. Trichlor, Dichlor, and calcium hypochlorite is 1 lb. per 10k.

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