Black tar substance around hot tub

[Luis]

I’ve had my spa for about 4 years that I bought at Homedepot online. It’s an American Spa, but there is a black tar substance that has been sticking above the waterline. It’s not mold nor any chemical imbalance. The water is clean and balanced. I have drained and clean spa several times already. I’ve also changed filter. I just recently checked the O Rings that are on each side of the heater tube and those are white and in good condition. My motor is not leaking so it can’t  be the rings. Anyone had this issue and if so what is it??

 

 

[CanadianSpaTech]

There are many other o-rings around the spa that might be deteriorating.. diverter valves, pump unions, pump wet end seals. If the spa has a "salt" system I have seen the sacrificial zinc anodes deteriorate and send black particulate into the water. Suggest you also run some Ahh-Some plumbing line cleaner next clean out to remove any film from the spas plumbing. Going to be a challenge to find out what the cause is but I would start with the o-rings around the valves and pump unions (heater might be white but pump union gaskets or o-rings might be black) first as they are cheap. 

Spa pillows can also be a source that should be looked at closely.

City or well water?

[Luis]

City water, but that has never effected anything in the home. We do have hard water but never seen anything like this. I’m going to take the spa pillows out, but I don’t see them gooey or deteriorating. I will try the

Ahh-Some, and as for the pump there isn’t any leakage.

Thank You for your response.

I will keep you posted and hopefully I can get to the bottom of this.

Can the diverters be an issue? I would figure that if they were the cause it would of been very minimal since the O-rings are small.

[RDspaguy]

@waterbear

[waterbear]

It's pretty hard to determine the source of a scum line without further information.

First, what sanitizer system are you using (chlorine, bromine, biquinde/peroxide, "mineral stick" with chlorine or bromine, ionizer. If you are using chlorine what type (trichlor, dichlor, liquid chlorine or bleach, calcium or lithium hypochlorite, salt water chlorine generator). If bromine are you using a one step or two step product, floater by itself, or one or two step with a floater. Are you using MPS to shock?

Do you have ozone?

You said it's not a chemical imbalance but I would be interested in your test results for the past few months, particularly pH and TA and how you test them.

@RDspaguyand @CanadianSpaTech I think you see where I am  going with this.

I have a few possibilities as to the source of your scum line but until I get some more information it's impossible to say what it might be.

[RDspaguy]

17 hours ago, waterbear said:

think you see where I am  going with this.

I think you give us too much credit, oh wise master of the chemical stuff.😆 I'm an electrician who answered the wrong job ad and ended up fixing spas. Don't expect me to keep up with you on this one my friend.

[CanadianSpaTech]

20 hours ago, waterbear said:

@RDspaguyand @CanadianSpaTech I think you see where I am  going with this.

I was going to one of us knows but it looks like the answer is closer to 0 🤷‍♂️

[waterbear]

Come on guys, it's staring you in the face!   I just need confirmation on the sanitizer used and the test results. Here's a hint, what can make o rings (and filter end caps and such) turn gummy and, if not, what can cause plastic to dissolve (and it's not the peroxide).

[CanadianSpaTech]

151 Rum and Coke? 🤣

[christopher5246]

I have a Dynasty spa which i have owned for approx 20 years.  I always use a liquid chlorinator by Pool Essentials but recently started using a 1 inch tablet chlorine tab in a floater. (the floater chlorine last longer) Over the past 30 days my spa pillows developed a tar substance which is very sticky and black junk appears on the tub near the edges of the pillow.  It is difficult to get off and i usually use a paint thinner to get it off.  I replaced 2 of the pillows and the new ones did the same thing within several days.   I suspect it is the pool chlorine tablets that are too strong and actually melting the pillow.  I have switched back to my old liquid chlorine to see if this is the case.  The chlorine levels tested fine each time, however, the PH dropped a bit.  Thoughts?  

[waterbear]

Chlorine tabs are trichlor and extremely acidic. They are not recommended for use in spas for this reason because of the small volume of water compared to pools which means pH is less stable than in a pool. They can and will cause ph to crash to dangerously low levels which can cause pump seals, o-rings, and other rubber and plastic parts to become damaged. The black junk you are seeing is probably from very low pH dissolving something in the workings of your spa. Trichlor goes in acidic and has an acidic reaction when it sanitizes. TA must be in the 100 to 150 ppm range when using it in a pool.

On the other hand, liquid chlorine is pH neutral on use. (goes in alkaline and had an acidic reaction when it sanitizes).

Also, continued use of trichlor WILL cause overstabilization, much like dichlor. Trichlor add 6 ppm Cyanuric acid (stabilizer) for every 10 ppm of chlorine added. Dchlor is even worse, adding 9 ppm Cyanuric acid for every 10 ppm chlorine.

Please post a full set of test results (FC, CC or TC, pH, TA, CH, and CYA) and how they were obtained (strips, liquid reagent test kit, strip reader or colorimeter and whether they were home tests or dealer tests and if possible, the brand (Taylor Technologies, LaMotte, Hach, AquaChek, etc.) so we can get a better idea of what's going on.

3 hours ago, christopher5246 said:

The chlorine levels tested fine each time, however, the PH dropped a bit. 

This tells us nothing about the condition of your water. Test result numbers do. For example, the chlorine level necessary for sanitation depends on the current cyanuric acid (stabilizer) level in the water.