Iron oxide--rust issue?

[Vesuvius]

After many months of a leaking tub, we finally got the issue resolved in the beginning of October and, in addition to fixing the leak by replacing the circulation pump and repairing some other minor issues, we had the heater replaced, as it was heavily rusted (I've been running a Saltron Mini salt tub since Feb '23). I noticed in my weekly maintenance afterward that every time I opened the cover, I found a couple of small collections of black grit collected at the bottom of the corner seats along one side of the spa. When this continued through the month, I thought it might be my Saltron cell nearing the end of its life with corrosion of the base metal, so I replaced this in late October. However, the issue has persisted. I think the grit is iron oxide/magnetite, as it leaves black streaks on the acrylic shell if rubbed against the shell when being vacuumed up. I'm wondering if I may have a continuing rust issue in one of my booster pumps (one of these pumps handles the side where the grit continues to collect). Does this make sense? If so, I'm assuming a replacement is the answer, right? Is there anything else metallic in a typical spa that could be rusting beyond the heater, circ pump and 2 booster pumps?

Thanks!

 

[ajw22]

Maybe @RDspaguy will have ideas when he wanders by.

 

[Vesuvius]

Thanks, Allen

 

[RDspaguy]

McCluer, '89.

think the grit is iron oxide/magnetite,

Does it stick to a magnet?

thought it might be my Saltron cell nearing the end of its life with corrosion of the base metal,

I have seen salt cells produce stains and particulate, though I don't know the cause.

I'm wondering if I may have a continuing rust issue in one of my booster pumps

There is only a very small piece of stainless steel (part of the shaft seal) exposed to water contact in the pump. This is probably not the issue.

Is there anything else metallic in a typical spa that could be rusting

No. Most metals in the water were there when you filled it up. Ph/alk, oxidation, and catalysts (heat, electricity) can cause disolved solids to come out of solution.
Heater failure, depending on severity, can put particulates in the water.
O-rings can deteriorate and release tiny specks of gooey rubber. Could it be that?
Replacing parts and especially cutting pipe or bending flex will cause any buildup in the pipes to crack, flake, or otherwise break loose and come out of the jets for weeks after a repair.
I'd suggest a purge with ahhsome and start fresh. If it continues did deeper, but it might be nothing.

 

[Vesuvius]

Thanks, RD. St. Charles West '87

Does it stick to a magnet?

Good question I should've thought of myself--no, it does not. But I now see from AI research that not all forms of iron oxide are magnetic so not sure what to make of that. Attached is a photo of some of it that I vacuumed out yesterday.

I have seen salt cells produce stains and particulate, though I don't know the cause.

I'm confident the Saltron's not the problem here, as I had none of this over the first year or so of using the Saltron and continue to have it every time the jets run well after putting in a new Saltron. However, the spa originally came with an in.clear salt cell (bromine system) that failed in Mar '21 and was left in-place (i.e. water continues to run through it) when I switched then to a chlorine sanitization approach. Could this old in-line cell be rusting or causing problems?

No. Most metals in the water were there when you filled it up. Ph/alk, oxidation, and catalysts (heat, electricity) can cause disolved solids to come out of solution.

It seems unlikely this is coming from the water, as this batch came from the same city water source I've always used (including for our pool) and I've never seen this issue before. Are you saying that spa booster pumps don't include metal components (e.g. motor, shaft, fittings, fasteners)? I'm a complete novice with this equipment stuff, but that would very, very much surprise me.

Heater failure, depending on severity, can put particulates in the water.

Per my OP, the original heater was heavily rusted when we replaced it mid-Sep. But I would think any residual particulate would've already worked its way through the system nearly 4 months after replacement, yes?

O-rings can deteriorate and release tiny specks of gooey rubber. Could it be that?

It's not gooey (firm, charcoal-like particles) and doesn't look like rubber (see photo).

Replacing parts and especially cutting pipe or bending flex will cause any buildup in the pipes to crack, flake, or otherwise break loose and come out of the jets for weeks after a repair.

The repair guy did replace a leaking pipe, but, again, it's been 3.5 months since that happened.

I'd suggest a purge with ahhsome and start fresh. If it continues did deeper, but it might be nothing.

I should've included this in my OP but I did do an Ahhsome purge/water change just after having all of the repairs done mid-Sep. So, if there was some post-repairs residual stuff in the pipes, that Ahhsome process should've wiped it out, yes?

Another piece of info--several of the silver-colored metal (I think they're metal?) nozzle covers under the water line are collecting what looks like rust on them (when I rub it off, it looks like reddish dust). Not sure if this is nozzle covers themselves rusting or whatever is coming through the pipes just collecting on them.

Appreciate your thoughts!

 

[RDspaguy]

Could this old in-line cell be rusting or causing problems?

Yes.

came from the same city water source

But variables such as ph and oxidation can cause dissolved solids to come out of solution. I know the water around StL, I worked there for the first half of my 27 years in this business, and it's loaded.

Are you saying that spa booster pumps don't include metal components

That contact water, I am. And the old ones that used metal used brass. It's not the pump, unless it's some manufacturing defect I can't imagine.

But I would think any residual particulate would've already worked its way through the system nearly 4 months after replacement, yes?

Depends on how much got locked into scale (calcium buildup from high ph/alk) or biofilm (chlorine resistant bacterial mass, common in spas). Debris can also build up behind the jets and slowly work it's way out.

Ahhsome should clear out anything remaining.

nozzle covers under the water line are collecting what looks like rust on them (when I rub it off, it looks like reddish dust). Not sure if this is nozzle covers themselves rusting or whatever is coming through the pipes just collecting on them.

Or dissolved solids. Those are usually stainless steel, though I have seen some that were chrome over an alloy. Stainless does rust, but it takes some pretty brutal conditions. It is not uncommon to see a stain at the heater return(s) and ozone/sanitizer return.

That looks like grit from asphalt roof tiles. Quite common in spas.

 

[Mdragger88]

That looks like grit from asphalt roof tiles. Quite common in spas.

This was my first thought looking at that last picture. I get some in my spa (carried in on our feet i assume) but not near that much. Maybe because we rinse our feet first as we enter?

 

[Vesuvius]

Thanks again, RD.

Recall that this problem is largely concentrated on 1 side of the spa that is serviced by 1 of the 2 booster pumps. This is what led to me to think I may have a rust issue in that pump. It is true that recently I'm seeing much, much smaller amounts on the other side as well but initially it was really only on the 1 side. This makes it unlikely that the in-line old cell is causing the issue, right?

Ditto on the dissolved solids. I highly doubt this is the issue, as I run very stable 50 TA and 7.4-7.7 pH, never have any CC, use AquaClarity weekly and have had only 4 man-hours of usage in the 3.5 months since the repairs/Ahhsome/refill. And, again, even it it was a dissolved solids issue, I'd think it would not be seen only on 1 side of the spa.

That looks like grit from asphalt roof tiles. Quite common in spas.

It does look similar in the photo but I don't how that could possibly be what it is. The thing is covered all the time (see above with how embarrassingly infrequently it gets used), is never uncovered in stormy conditions and we've not had any roof work done in years.

Soooo, pulling all of this info together (including the largely 1-sided nature of the problem), what's your remote diagnosis?

 

[RDspaguy]

Soooo, pulling all of this info together (including the largely 1-sided nature of the problem), what's your remote diagnosis?

Don't have one. Get that old cell out. The rest of my advice I will dm you.