Hiring out a hot tub - an easy chemical regime?

Wmrstafford

Member
Aug 8, 2018
7
UK
Hi guys 'n' girls!

I've just started to hire out an inflatable hot tub. Following what other hirers do, I've been placing 2 small chlorine tablets in the floater and if higher bathing loads are applicable I have advised them to add a third tablet after the first soak.

Whilst this regime certainly works well enough to not have any major problems, I still collect the hot tub after 3 days and the water is never as clear as I would like.

I'm going to be changing the way I do things now, and the following will apply....

1. Hot tub will be setup and filled to 37C using a portable gas water heater so that it can be used the same day.
2. I intend to only offer 2 day hires - so long term water chemistry is not important.
3. Between hires, the hot tub will be thoroughly disinfected and cleaned.

My thoughts of options are....

1. Start the hot tub up with a 5ppm dose of dichlor granules. Place 2 chlorine tablets in the floater and tell them to place it in the water after their first soak etc.
2. As above, but use bromine?
3. Use a startup dose of bromine and then provide MPS shock only with instructions to add it after each soak (to reactivate the bromamines into bromine)

Test stripping theoretically shouldn't be TOO essential for just 2 days of use starting with a thoroughly cleaned tub. Most hirers around here dont give out test strips and to be honest I doubt the average user would be able to accurately read them. I therefore think it's about finding a simple routine for just 2 days use, whereby nobody is going to be superchlorinated to death but there's going to be enough oxidation going on for nobody to be able to fall ill with just a couple of days from start to finish.

I'd be interested to hear peoples thoughts on a regime. Of course if there is anyone already in the hire business then I'd be keen to know your own methods too.

Thanks for your time
 

Wmrstafford

Member
Aug 8, 2018
7
UK
I've also come across the following document, and page 2 is supposed to be someones instructions that has been in the business for a couple of years and hasn't had any known issues.
https://www.bishta.co.uk/wp-content/uploads/2013/12/M007-Hire-or-Rental-of-Hot-Tubs.pdf

That doesn't, of course, mean it's what I should necessarily do. I would prefer some advice here if you lovely people don't mind.

- - - Updated - - -

I've also come across the following document, and page 2 is supposed to be someones instructions that has been in the business for a couple of years and hasn't had any known issues.
https://www.bishta.co.uk/wp-content/uploads/2013/12/M007-Hire-or-Rental-of-Hot-Tubs.pdf

That doesn't, of course, mean it's what I should necessarily do. I would prefer some advice here if you lovely people don't mind.
 

Wmrstafford

Member
Aug 8, 2018
7
UK
Continuing my own thoughts whilst hoping for some replies here.

I've been reading about using bromine and quite like the way it works vs. chlorine. If I started with a bromide bank of 30ppm and added enough chlorine to activate 10ppm bromine, then provided users a set amount of MPS shock to add after each use would that work? Or in the case of 1 or 2 day hires is this a pointless method?
Or start with the 30ppm bromide and provide bromine tablets in a dispenser (which I know also contain chlorine as an activator)
I know it would be slightly more costly (although not much), and especially as it's only a day or two I'm thinking that it lessens the worry about any slight pH fluctuation as bromine is more effective across a wider pH range.

Please, somebody chime in! I'm driving myself mad with thoughts here :D
 

mknauss

Mod Squad
TFP Expert
May 3, 2014
13,964
Laughlin, NV
Welcome to the forum! :handshake:

I would suspect you are getting no responses as most members, and especially me, have never heard of what you are proposing!! Seems quite odd and kind of weird, but I guess each country has their own ways.

I would say use chlorine. It is simple and since you dispose of the water after a couple days, little issue.
 

Wmrstafford

Member
Aug 8, 2018
7
UK
Thanks mknauss! I started to think I had broken some rule about early posting ;)

Yes, here in the UK (or at least the not so wealthy parts), inflatable hot tub hire is massively popular. Some people also like to hire and try before thinking of buying their own. But in most cases it's simply a treat for a partner's birthday, a hen night with the girls or even a kids birthday.

Obviously, start-up shock dosing isn't an option as there's no time to wait 24 hours for the FC level to drop, so I think alot of hirers just chuck 2 or 3 trichlor tablets (small type) into a floater and leave them to it.

I'm leaning towards using dichlor granules only and starting off with 2 tsp which would give a 5ppm FC reading, and then just telling them to add 1tsp per hour of use when they think they won't be going in it again for at least an hour or two. Obviously based on the 3.5tsp per person / hour this is no way near enough for long term hot tub happiness, but I think it should be enough to not cause serious health risks for a maximum of 48 hours use before dumping. Also, there's a chance that people will decide 30 minutes later to use it again, so I wouldn't want to risk them putting in a massive dose in one go.

I realise that when I go to collect the tub, there could be nasties already lurking in the pipes etc and that FC is likely to be ZERO on heavy use occasions, but with a super-chlorinating method of cleaning the tub back at my home before the next hire (20ppm FC circulated for a couple of hours) I guess it should be all good.

I don't want to over-complicate it for the user but want the routine to be highly effective at providing a minimal level of sanitation. Most hirers only offer 3+ days of hire, whereas I'm going for the 1 or 2 day only option to further ensure a trouble free hire. There's nothing worse than collecting a tub after 4 or 5 days only to see that the water looks like something you wouldn't bathe your worst enemy in. It's that kind of reputation I'm hoping to avoid.
 

PoolguyinCT

In The Industry
Jul 21, 2014
2,848
Connecticut
A friend of mine was renting soft tubs from his store, then he found out a renting customer was a midwife & renting for childbirths..
 

ant 83

Well-known member
Nov 3, 2015
190
appleton wisconsin
I'd suggest using the small trichlor pucks, in an adjustable floater. New water with no CYA dosn't need very much chlorine to stay clear. The puck will release chlorine slow and steady, keeping the water nice.

The downside of course is that trichor is quite acidic. So you'll need to set the TA in the upper ranges (80-90 I'd think), and limit how fast the puck dissolves with the floater. This won't be enough chlorine to keep up with heavy spa use.

I'd recommend giving the spa users some liquid chlorine to add on a schedule like what is in your link. Liquid chlorine effects PH less than all the other available chlorine sources, and is easy to use, so that's why I recommend it.

The problem with liquid chlorine is people don't like it in my experience. People were freaking out about my dog drinking the spa water the other day. OH NO DON"T DRINK WATER WITH CHLORINE IN IT. sigh. (every heard of cholera? no? wanna know why?)

Anyway, I suppose calhypo would be more acceptable to the public, and would offset somewhat the acidity of the trichlor. Ive never used it though, but I'm pretty sure it needs to be premixed/dissolved in a bucket before adding. That sounds inconvenient to me compared to measuring out a half cup (or whatever) of bleach.

Anyway, it's probably folly to expect your spa renters to do any testing. People just won't do it.

But having a chunk of trichlor dissolving, with some additions of bleach/cal-hypo, while the spa is in use, would seem to be pretty fool proof to me.

A peristaltic pump metering out bleach on a timer that runs while the spa is in use would remove the human failing to add factor. A drop in SWG would be another option.

Do us a favor and check back in, and let us know what works best for your situation.

Oh, and I will just add this in case you haven't seen it, or don't know: https://www.troublefreepool.com/threads/17723-Certified-Pool-Operator-(CPO)-training-What-is-not-taught
Effects From Different Sources of Chlorine
The following are chemical facts independent of concentration of product or of pool or spa size [EDIT] (added info on affect on TA after accounting for chlorine addition and usage/consumption): [END-EDIT]

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6.1 ppm and decreases Total Alkalinity (TA) by 7.1 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9.1 ppm and decreases TA by 3.5 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm and increases TA by about 0.4 ppm.
For every 10 ppm FC added by ANY source of chlorine, there will be 8.2 ppm salt from when the chlorine gets used/consumed and converts to chloride. For bleach, chlorinating liquid, and lithium hypochlorite, there is an additional 8.2 ppm salt added upon addition so the net result is 16.5 ppm salt from these sources and the TA rises by 0.1-0.6 ppm depending on the amount of "excess lye" in the product.
 
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