PVC flex tube: brittle and with corrugated interior

[RuiP]

Hi

This is how I found the interior of a PVC flex pipe connecting to the bottom of a skimmer:


It had a smooth interior surface when it was new, right?
In addition, the tubing was very brittle: I was able to break it in 2, by hand.


It's a 8 year old pool, with chlorine treatment, and water heated to around 30ºC (86ºF). Maximum temperature it ever had was probably 33ºC (91ºF)
What can cause this?
- Too much heat?
- Too much chlorine. At times the pool spent a few months without water circulation; and that tube was connected to a skimmer with the chlorine tabs.
- Subpar material/tubing?

Thanks!!

 

[JamesW]

At times the pool spent a few months without water circulation; and that tube was connected to a skimmer with the chlorine tabs.

That is the cause of the damage.

 

[Toxophilite]

When I was a young mechanic, we kept a 55 gallon drum of muriatic, straight, to clean brass marine pump housings and other parts. Whenever a customer left a PVC fitting in their pump, we let the muriatic loosen it. That's exactly how it would come out of the barrel after a day or so soaking. Turns it to rubber. Any chance you once added acid without adequate circulation and it slugged into the drain and sat there?

 

[JamesW]

Trichlor is very acidic.

 

[RuiP]

That is the cause of the damage.

Thanks for the quick reply!
Since now I have the pool pump connected to my home automation (Home Assistant), I'll make sure the pool pump will run for a couple of minutes every X hours, to avoid excessive chemical concentration on the skimmers/pipes.

When I was a young mechanic, we kept a 55 gallon drum of muriatic, straight, to clean brass marine pump housings and other parts. Whenever a customer left a PVC fitting in their pump, we let the muriatic loosen it. That's exactly how it would come out of the barrel after a day or so soaking. Turns it to rubber. Any chance you once added acid without adequate circulation and it slugged into the drain and sat there?

Apparently I may have done that (invertedly) by letting the pool pump to be shut off for long periods of time.... lesson learned.

 

[JoyfulNoise]

You shouldn't be putting trichlor tablets, or any chemicals for that matter, in the skimmer anyway. Use a blue plastic chemical floater if you have to OR, better yet, switch to liquid chlorine or a salt water chlorine generator.

 

[JamesW]

If you have a variable speed pump, you should let it run continuously at low speed.

As long as the water continues to flow, the levels should not get to dangerous or corrosive levels.

If there is no heater, I would probably be ok with a few tabs in the skimmer as long as the pump does not stop.

As soon as the pump stops, the water begins to drop in pH and the chlorine goes very high.

It's a lot like a 400,000 btu/hr gas heater.

400,000 btu/hr is a lot of heat being added, but as long as you have 40 GPM, everything is fine.

If the water flow stops, even for a few seconds, the heat increases the water temperature to dangerous and damaging levels.

 

[RuiP]

You shouldn't be putting trichlor tablets, or any chemicals for that matter, in the skimmer anyway. Use a blue plastic chemical floater if you have to OR, better yet, switch to liquid chlorine or a salt water chlorine generator.

I can't use the floater because I have a floating pool cover (had a floater in the past; before I had the pool cover).
I could switch to salt water, but I would need to replace my heat exchangers (for the solar hot water; and for the house heat pump) from steel to titanium... and that would be a bit expensive.

Will look into the liquid chlorine option, though!

 

[1poolman1]

Thanks for the quick reply!
Since now I have the pool pump connected to my home automation (Home Assistant), I'll make sure the pool pump will run for a couple of minutes every X hours, to avoid excessive chemical concentration on the skimmers/pipes.



Apparently I may have done that (invertedly) by letting the pool pump to be shut off for long periods of time.... lesson learned.

There are two types of people that love you to put tablets in a skimmer; those who replace skimmers and underground plumbing and those who replace pool pumps. Get a floater or run the pump 24/7 if you continue to do that. Despite the fact that many times 3" tri-chlor tabs are packaged as "skimmer tablets," THEY ARE NOT.

 

[JamesW]

(3) 7 oz tabs in a skimmer at 20 gpm will raise the FC by 5 ppm, lower the TA by 3.5 ppm and lower the pH by 0.27 from the pool level to the downstream level.

This assumes that the tabs fully dissolve in 24 hours.

Tabs can last typically 2 to 5 days, so the above case is a worst case scenario.

At longer times for full dissolution, the chemistry change is less according to the amount of time it takes for the tabs to fully dissolve.

So, if the water before the skimmer is 5 ppm fc, 80 TA and 7.8 pH.

The numbers downstream are 10 ppm FC, 76.5 TA and 7.53 pH.

If there is no heater and the water stays moving continuously, I think that you can use up to (1) 7 oz tab per 7 gpm in the skimmer.

Typically, I would not recommend tabs in a skimmer for most people most of the time, but I think that it is not dangerous as long as you keep the water moving.

 

[JoyfulNoise]

I was at a pool party once and I noticed that the skimmer had three trichlor pucks sitting on the ledge of skimmer intake. Presumably the pool guy did this to avoid them sitting in the skimmer and causing problems. I asked the pool owner what they were (I knew what they were but I was playing dumb … ok, maybe I wasn’t “playing” …) and she replied, “I think it’s chlorine or acid or something for the pool chemicals, I dunno exactly but the pool guy always leaves them there …” .

My two takeaways from that conversation were -

1. Most homeowners know nothing about the pools they own;

2. Sometimes pool guys find ingenious ways to work around problems.

 

[JamesW]

In general, I don’t recommend putting tabs in a skimmer as there are things that can go wrong.

My main point is that as long as water is moving, the chemistry does not get bad or corrosive.

Floaters can have problems and inline and offline feeders can also have problems.

Overall, trichlor tabs tend to be problems in multiple different ways.

They can be useful in some cases, but you really have to be careful with them to avoid problems.

 

[Newdude]

Have you all hugged your SWGs today? (For those that have them)

 

[JamesW]

The biggest danger is when the water flow stops and the chemicals get concentrated.

The second biggest risk is when people forget about testing and the TA and pH crash and the TA gets to 0 and the pH gets to 4.5 and the low pH and chlorine oxidize the copper in heat exchangers and causes other damage as well.