Gray Scum/Bio Film

[GregD]

Hey all,
Thanks for the recent add.

I am the owner of a new Hot Prings Pulse, so far we are very happy with this tub. In the past we owned a Sundance spa. The hot springs seems to have better filtration and much more options in the way of pump speeds and jet functions. The addition of the blue tooth stereo was a promo at the time of purchase and has been a big hit so far. From music or watching TV/movies via my I-Pad.

So, on to my question. After approx 90 days of use and getting used to the spa water chemistry. I have been plagued with a light gray scum line. I understand that this is a build up of organic solids/waste. However it is unpleasant and I am a bit of a water quality freak.

What do you all recommend to combat this issue?
Am I doing something wrong with water maintenance? (2oz shock after every use and 5oz every sat to sanitize. Also add algicide as an precaution. Tub equipped with O.Z.)

Thanks in advance
GregD

[Jacuzzi Jim]

 If it's been 90 days and a lot of use I would drain it and re-fill.   Not sure why you are using an algaecide unless you are leaving it uncovered in the sun for long periods?   Even then using chlorine, algae should not be a problem.    As far as the scum goes you could try an enzyme type product once week it might help. 

 You under any water restrictions?   

[kingdarb]

I would drain and refill after 90 days.

[GregD]

Thanks for the replies.
I will plan to drain the tub and refill with a inline filter to collects any un-wanted minerals from my well.

The algaecide being used is from Spa Pure (spa pure simply soft). I add this at the same rate as my Multi Shock. This was the recommendation from my retailer.
Thoughts on this practice?

G

[HotTubLover57]

It is unnecessary to use the algaecide if you have a proper sanitizing system.

Bromine tablets are better than chlorine (which doesn't come in tablet form) for hot tubs.

[Sam]

Algae requires sunlight to grow.  If you leave the spa covered the majority of the time (as most people do), there is no need to add algaecide.

[Jacuzzi Jim]

It is unnecessary to use the algaecide if you have a proper sanitizing system.

Bromine tablets are better than chlorine for hot tubs.

 Why is that?

[kingdarb]

I've only had a tub for about four months, the chemicals the dealer sold me are basically a three month supply of everything that is needed.  It is called the "Pro" kit by Sani Marc.  It is a dichlor system and the dichlor comes in tablet form.  The hot tub store and the kit itself just recommends dropping the tablet into the tub with the pump running on low.  It dissolves in about ten minutes. 

I've never used Bromine, but I understand that it is slightly less maintenance.  That said I have just followed the directions that came with my kit and the water has been crystal clear for three months with two adults using the tub about five times per week for 20-30 min each time.

It is unnecessary to use the algaecide if you have a proper sanitizing system.

Bromine tablets are better than chlorine (which doesn't come in tablet form) for hot tubs.

[chem geek]

It's interesting that Sani-Marc makes Dichlor tablets because I didn't think anyone did that, but of course any solid can be compressed into a tablet.  As you've seen, it dissolves quickly so it's basically the same as adding Dichlor granular to the spa.

The main problem with Dichlor is that it builds up CYA in the water and since the active chorine level is proportional to the FC/CYA ratio, there is less active chlorine over time and the oxidation and disinfection rates drop as a result.

What is the size in gallons of your hot tub?  The standard Water Replacement Interval (WRI) formula converted to person-hours is the following:

WRI (days) = (1/9) x (Spa Size in Gallons) / (# of person-hours per day)

So if you only had a 350 gallon spa then that would be (1/9) x (350) / (2*(25/60)*(5/7)) = 65 days

So you may have a larger spa size if you aren't finding the water getting dull in that time.  Either that or there are other parts of the Sani-Marc system you are adding to help keep the water clear (perhaps enzymes).  If you were to use the Dichlor-then-bleach method, then you could expect to keep the water clear for at least twice as long or 130 days (over 4 months) and it would be a lot less expensive, but if you are happy with your system and don't mind what you pay for it, then stick with it.

[kingdarb]

Hey Chem Geek,

My spa is actually on the smaller size of things.  It is a Bullfrog R6 and is 349 gallons. 

The kit that the dealer sold to me is supposed to run for 90 days without changing the water.  h ttp://www.sanimarcpro.com/en/

Basically the process is this:  One day 90 (when water is supposed to be changed) you pour the bottle of EZ flush into the spa and run three filter cycles.  This is supposed to clear accumulated stuff out of the plumbing.  Then drain and clean the tub.  Then refill.  Once refilled, put Spanaturally in filter compartment (this looks like an algae strip contained in a mesh bag - supposed to stop formation of micro-organisms).  This strip is replaced every month.  Also on initial fill, pour 1/3 bottle of EZ start into water (this is supposed to destroy organic matter in tub and 1/3 of bottle is poured in every month for the three month cycle).  Also on initial fill, add a dichlor tablet.

After that, the program is to add a pre-measured package of shock two days after dichlor tablet (shock looks to contain dichlor).  Then once a week, you continue with the dichlor then shock two days later for the duration of the program.  They also recommend adding extra dichlor after heavy use (parties etc) and some extra tabs are included for this.

What I have found with this is that there usually is chlorine in the tub (sometimes it seems to drop as low as 1ppm), but chlorine can also get high when the dichlor tab is added or the shock is added (I am using test strips to measure but have a proper kit on order).  My water has always been crystal clear and never gross smelling, but it can get a chlorine smell from time to time.  This has never been overpowering or irritating and generally goes away after shocking.  The CYA level has risen high.  I am almost at day 90 and the test strips indicate that my CYA level is somewhere between 150-300 ppm. 

I am a new hot tub owner and know very little about water chemistry (trying to learn as I go on) and the dealer suggested this kit to me as an easy to use program, which it has been.  That said, the more I am learning, the more I am thinking that the CYA level might be an issue.  Perhaps the Spanaturally strips and the EZ start help with this.  I have noticed also that in month 2 and 3 that when I initially add the EZ start liquid that the water is crystal clear at rest but can become cloudy when the pump is running on high.  I am guessing that this is due to the EZ start and the cloudiness dissipates as soon as the jets stop.  This also stops happening as the month progresses.

On the initial fill I had to add some calcium and I have had to add some alkalinity on two or three occasions over the course of the last three months.

I am not married to this sanitation program by any means, and I am certainly open to trying the bleach/dichlor method.  This Pro Kit that I have been using costs about 80 bucks for three months.  I am guessing bleach/dichlor costs less, and it is not a problem with me to test and add sanitizer daily.  I am just not sure if I should be worried about dissolved solids and salt produced from using the bleach, and if that will damage anything or void my warranty.

It's interesting that Sani-Marc makes Dichlor tablets because I didn't think anyone did that, but of course any solid can be compressed into a tablet.  As you've seen, it dissolves quickly so it's basically the same as adding Dichlor granular to the spa.

The main problem with Dichlor is that it builds up CYA in the water and since the active chorine level is proportional to the FC/CYA ratio, there is less active chlorine over time and the oxidation and disinfection rates drop as a result.

What is the size in gallons of your hot tub?  The standard Water Replacement Interval (WRI) formula converted to person-hours is the following:

WRI (days) = (1/9) x (Spa Size in Gallons) / (# of person-hours per day)

So if you only had a 350 gallon spa then that would be (1/9) x (350) / (2*(25/60)*(5/7)) = 65 days

So you may have a larger spa size if you aren't finding the water getting dull in that time.  Either that or there are other parts of the Sani-Marc system you are adding to help keep the water clear (perhaps enzymes).  If you were to use the Dichlor-then-bleach method, then you could expect to keep the water clear for at least twice as long or 130 days (over 4 months) and it would be a lot less expensive, but if you are happy with your system and don't mind what you pay for it, then stick with it.

[chem geek]

ALL forms of chlorine add salt because when the chlorine is used/consumed it becomes chloride salt.  The difference is that with Dichlor it also adds Cyanuric Acid (CYA) while with bleach it does not but adds additional salt upon addition.  For every 10 ppm FC added by chlorinating liquid or bleach (or lithium hypochlorite as well) it also increases sodium chloride salt by 16.5 ppm after accounting for chlorine usage/consumption.  With Dichlor, for every 10 ppm FC is adds 9 ppm CYA and 8.25 ppm sodium chloride salt after accounting for chlorine usage/consumption.  The CYA buildup is worse than the salt buildup since 100 ppm CYA is significant while 200 vs. 100 ppm salt is not.

[kingdarb]

Ok thanks.  I think I may give this a shot then.  I am picking TF-100 test kit next week and I am due for a water change.  Once the water change is done, I may start doing the dichlor then bleach method.

Thanks for the info chemgeek.  You are very helpful!

ALL forms of chlorine add salt because when the chlorine is used/consumed it becomes chloride salt.  The difference is that with Dichlor it also adds Cyanuric Acid (CYA) while with bleach it does not but adds additional salt upon addition.  For every 10 ppm FC added by chlorinating liquid or bleach (or lithium hypochlorite as well) it also increases sodium chloride salt by 16.5 ppm after accounting for chlorine usage/consumption.  With Dichlor, for every 10 ppm FC is adds 9 ppm CYA and 8.25 ppm sodium chloride salt after accounting for chlorine usage/consumption.  The CYA buildup is worse than the salt buildup since 100 ppm CYA is significant while 200 vs. 100 ppm salt is not.