Calling All Hot Tub/Spa Owners (and Chemists)

[rp2813]

I have an above ground spa that is over 20 years old. It has been in nearly continuous operation over that time period, since it's 120V and takes almost 24 hours to heat up so we just keep it running. I believe this regular exercise has helped the tub's systems last as long as they have. About two years ago, the original heating element went out and I was lucky enough to find a replacement element. Well, the new element has already failed. The repair guy came out and said he's never seen one so badly corroded. So I asked him how this could happen when the old one lasted 10 times longer. He advised that the pH being slightly off for even a short time can trigger an irreversible process of deterioration. I tend not to buy that, considering I didn't know what I was doing when we first moved in to our place and the chemicals were way off a lot of the time. Yet the element lasted another 15 years before failing.

Does anyone have any ideas on what else could have caused such an early failure due to serious corrosion? Maybe it was just a cheap part? I don't want to be doing this again in 2 years, and both times the element has failed it happens in winter when I tend to use the tub a lot more. Perhaps there's an additive I can use that will protect the element? Any help on this matter would be appreciated.

Ralph

 

[goatfarmer]

We've changed the heater in our tub twice in about 15 years. The first one lasted a good 10 years, the second about 4. Chemicals being off balance is probably why they deteriorated, although our heaters were stainless steel. I don't know of any additives that would help protect the heater. In your case, it's also possible the second heater had a defect in it.

kennyGF

 

[rp2813]

Thanks Kenny. I'm thinking it's probably a defect thing too. This should come as no surprise to anyone here, as it's very likely that just like automatic washers, heating elements aren't made to last like they used to be.

 

[sudsmaster]

You probably need to get a spa/pool water quality kit, which will enable you to check the pH, disinfectant levels, etc. If you can find a kit that merely has you dip a stip of indicator papers into the water, that would be quickest, but probably not the most accurate. But better than nothing.

I'm wondering if the replacement element was made overseas and not up to the quality of the original US-made element.

Also, chlorine and sodium chloride is the enemy of most stainless steel alloys.

Just wondering... if you keep this thing running and heated all the time, your electric bills must be "up there"... no?

 

[goatfarmer]

Our spa is a Great Lakes brand, and it has a position where it "idles", so to speak. It keeps the heat on, and the water circulating, but not at full speed. Operates on a timer, which in the winter, is 24 hrs. During warmer months, it only operates about 7-8 hrs, unless someone is in it.

 

[rp2813]

The cost to run the tub 24/7 isn't that bad. When we moved in 17 years ago, it was about $20 a month. At the time, that amount was less than the cost of a one-hour tub rental for two at the local spa. The monthly cost has gone up from there over the years but we use the tub a lot so it's a bargain compared to paying for tub rental (which I presume has also gone up) and it's way more convenient. We balance things out a bit with a gas dryer instead of electric, we have a gas stove, and like the vast majority of people in the Bay Area have a gas water heater.

I feel this is a case of inferior parts. I only use bromine tabs in a floating erosion dispenser, never chlorine, and I keep on top of the pH. I've used other products such as "Spa Defender" and "Metal Gone" but the repair guy has advised that those additives aren't needed if the bromine and pH are kept at correct levels.

One thing is for certain. If this happens again in two years, I'll be doing the job myself and tracking down a heating element made by a different manufacturer.

 

[sudsmaster]

Chemically speaking, bromine is very close to chlorine. But I haven't researched its effect on stainless steel. Most of the stuff I've read deals with chlorine, probably because it's much more common (in the form of table salt, sea water, etc).

What it sounds like you have is a two speed spa pump. I run a two speed spa pump (Hayward) for my koi pond. It runs 7x24, at low speed, and I have estimated its power consumption at about 150 watts. That is roughly equivalent to a couple of modern full size refrigerators... about 1,300 Kwh/year. I figure it costs me between $10 and $20 per month (depending on which rate you pick). The pond is not heated. I use the high pump speed when back flushing the bio-filter. I figure the pond pump alone is responsible for about 100 Kwh/month, which is enough to send my consumption into the higher $.20/Kwh tier. Oh, well, I don't want the fish to die, so I live with the expense. The plus side is that when I talked to the Hayward company, they said that since it's running almost always on low speed, the pump and motor should last a very long time.

 

[sudsmaster]

Bromine is corrosive to stainless steel

Not too surprising considering its chemical similarity to chlorine.

http://www.recreonics.com/fyi/stainless_steel_maintenance.htm

 

[rp2813]

Thanks Rich. I'm wondering if the link you provided is only addressing stainless steel that's exposed to the elements, which may provide better conditions for corrosion as opposed to stainless that is constantly submerged, which would be the case with the heating coil/element. But I'm far from being a chemist or scientist. At this point, I'm going to change out my filter also and start out with everything new once the replacement heater is installed. It could be that the old filter is retaining some bad chemical stuff that a good jetting with a nozzle can't get rid of completely. Supposedly bromine is better for your skin and that is why I prefer it over chlorine.

Our tub is also running 24/7 with a Hayward pump, has been for 17 years, and I do believe that's why it has lasted as long as it has. It's 120V and takes almost 24 hours for it to heat up so rather than plan for a dip 24 hours in advance we just leave it running and it's always at about 104. It really helps on cold winter nights to get out there and raise your body temperature. Then when you get back in the house, 65 degrees is downright comfortable.

 

[goatfarmer]

If you decide to change the heater yourself, it's really not too bad of a job. I did the last one on ours. It's a pump made by Brett Industries, and the heater is right up front, underneath the pump.

 

[rp2813]

Yes, the heater is right up front on mine. I just got burnt out after thinking I had fixed the problem by replacing some crispy wires related to the heating system on the control panel. I put everything back together, filled the tub and started the pump and all was well. Until I realized I hadn't plugged the heater's cord into the panel. As soon as I did that, the breaker tripped. It was at the end of my week off from work and I wasn't going to have time to deal with pulling the whole heater out. Should there be a next time, I intend to do it myself and will do my best to locate a heating element that will hold up for more than just a couple of years. I have to believe I got an inferior product last time I went through this.

 

[sudsmaster]

Well, as I understand it, the corrosiveness of chlorine or bromine solutions is directly related to the concentration. This is why one should not add salt to a pot of water your going to bring to a boil, unless you take the time to stir it in and get it dissolved. Otherwise the grains will settle on the bottom of the pot, and as the metal warms up the chloride part of the concentrated saline around each grain will attack the protective chromium oxide layer on the surface of the stainless, and inititate a chain of events that can result in pitting of the surface. Similarly, if a salt or bleach solution is left to dry on a stainless surface, the salt or chlorine concentration will go up as the droplets evaporate - potentially leading to a highly concentrated tiny droplet that will also attack the alloy, resulting in pitting and possibly pinholes.

If your spa is always filled so that the heating element is covered, and you're not dumping a lot of undissolved bleach powder on the element, then obviously salt grains and drying out of salt or bleach droplets isn't a problem.

 

[rp2813]

I know. The heating element is always surrounded by water even when the tub is supposedly completely drained because it's in the lowest part of the piping. That's why I think I got a bad element last time. The bromine levels can sometimes get a little higher than midrange but they are always within the "ideal" range on the testing kit.

Thanks for all of the input guys. I'll just have to wait and see if the new element lasts any longer than its predecessor. I honestly don't think it has anything to do with chemical balancing since I stay on top of that and the original element lasted for a good 15 years.