Help / advice with cleaning tub for a newbie

[mrDT]

Hello forum

I bought a used hot tub a few weeks ago,
its a UK model 'Blue Whale Spa' 'santa anna' with 3 pumps and a balboa control system, about 4-5 years old.
It appeared to be in good condition - everything working and certainly looks the part.

As it's used I wanted to do a very good job ensuring its clean for its new users (the family).

I bought some 'pro-kleen' hot tub flush and filled the tub, ran it for 30 mins then drained it. There was yellow gunk on top of the foam when it did this.
so I drained it and then cleaned it down inside, then filled the tub and added some shock & chlorine to balance the water.

After a week or two the water was starting to look / smell (wet dog) not ok so I drained the tub and flushed it again, same yellow gunk on the foam, I also cleaned the filter and let it stand in bleach overnight.

I then wanted to be 100% sure it was clean so I added 1/2 gallon (3 litres) of thick bleach and ran the jets for a hour or two. (Possibly overkill)

then drained, then flushed again with the 'pro-kleen' and I am still getting the yellow gunk!
So drained and filled then flushed again - still some gunk on the foam.

Should I be aiming for no yellow gunk when it's flushed? What's others experience with cleaning / flushing the tubs?

Any advice or tips are much appreciated y'all

[kennethogden]

First get your chlorine high (about 10 PPM) and use Ahh-Some to break down the biofilms.
Place the filters (inside the hot tub while the purge is taking place).  Let the Ahh-Some seep deep into the pleats to remove whatever nasties are harboring inside.  Hose them off before you place them inside the tub that is filled with hot water.  Hose them off after the purge is done, usually less than 30 minutes.  Be sure to NOT use more Ahh-Some gel than what we say.  More is NOT better.  Lastly, when you see the brown detritus gunk that is removed from the plumbing be sure to wipe it off with a micro-fiber cloth so it doesn't cake and adhere to the acrylic surface.  Remove any removable pillows before the purge is started. 

[mrDT]

So i keep draining and refilling - then putting system flush in - each time there is yellow gunk!
This tub must be dirty!

[kennethogden]

re: "I bought a used hot tub a few weeks ago".   

Depending on how well maintained by the previous owner, it may take a few purges.

https://boisediesel.com/blog/2016/7/spa-purge  did a nice write comparing many different products.  Many of them aren't worth the time. 

[mrDT]

a good read - thanks for that
The fifth flush took place last night with the 'pro-kleen' hot tub flush - its very popular here in the UK.
I have ordered some ahh-some and will report once it arrives and I flush it in a few days.
its not cheap but hopefully works wonders.

[Red MC]

Perhaps the yellow gunk is coming from your water, and not some residual substance in the plumbing left over from the previous owner.  My suggestion is to let the filters do their work for a week, then clean the filters and see if you still get foam and yellow gunk when you run the jets.  During the week, check free chlorine daily and keep it around or above 3 ppm.  That should prevent the "wet dog" smell and green color.  It's common for a hot tub to consume a lot of sanitizer for a few days after a fresh fill.