New Fiberglass Pool Owner Questions

[DonD]

I am purchasing a house with a fiberglass pool. I have some experience with regular gunite pools but it has been a while.

I have not moved in yet and I do not know the total gallons or filter type yet. I do know it has a variable speed pump.

1st Question - I know the light does not work and I will need to replace it. I have replaced lights and light fixtures in other pools but do not know if the light fixtures are different in a fiberglass pool. Any help and or guidance with this would be appreciated.

2nd Question - What are the chemical challenges with a fiberglass pool and what should be my main concerns to watch out for?

3rd question - Are there any books or videos that cover the basics of fiberglass pools? I don't know how much if any they vary from gunite pools to take care of?

All advice and ideas are appreciated - Thank You!

[Teapot]

Welcome,
1. Whilst some fittings do vary the general light niche fittings are roughly the same. If you are replacing may I suggest LED version this time. Replacements are made to fit existing niches.
2. No real chemical issues, you won't have to worry about water hardness or alkalinity as you would with gunite. That would still require a decent test kit and not dip strips.

3. So much of what is written and on you tube is wrong/out of date, stick around here and we will help.

Fantastic that you have a variable speed pump, look forward to hearing about the rest soon.

[Denniswiseman]

One thing to watch out for is iron in the water as it will stain
Also be careful about draining down if you don't have a hydrostatic valve in the main drain as ground water can make it float

[Teapot]

One thing to watch out for is iron in the water as it will stain
Also be careful about draining down if you don't have a hydrostatic valve in the main drain as ground water can make it float

Would that be any different to gunite Dennis (iron), in fact the higher pH of the gunite wall is more likely to cause any metal to drop out of solution unlike plastic.

They aren't called boat pools for nothing! Depends on the water table locally of course. If emptying, make sure the water is ejected a good distance away though.

[Denniswiseman]

One thing to watch out for is iron in the water as it will stain
Also be careful about draining down if you don't have a hydrostatic valve in the main drain as ground water can make it float

Would that be any different to gunite Dennis (iron), in fact the higher pH of the gunite wall is more likely to cause any metal to drop out of solution unlike plastic.

They aren't called boat pools for nothing! Depends on the water table locally of course. If emptying, make sure the water is ejected a good distance away though.

The reason why I mentioned it is that I have suffered from both quite badly

[Teapot]

No problem Dennis, what was the source of your iron staining?
One of my customers in the Dordogne has such soft water any iron/steel screw corrodes so easily it gave them annual problems which I had to
a: cure.
b: constantly remind them to change to stainless steel fixings everywhere.

[Denniswiseman]

No problem Dennis, what was the source of your iron staining?
One of my customers in the Dordogne has such soft water any iron/steel screw corrodes so easily it gave them annual problems which I had to
a: cure.
b: constantly remind them to change to stainless steel fixings everywhere.

No idea, it looked terrible so I did an ascorbic acid treatment and an underwater acid wash which cleared up the most of it
It was slowly coming back so another AA which cleared it all
I now reguararly dose with a sequesterant

[Teapot]

Hi Dennis, who's glass media are you using for filtration?
AA treatment just changes the form of the iron from Fe3+ to Fe2+ it just get re oxidised back to Fe3+ with the addition of an oxidiser like chlorine. Sequestrant just chelates it (binds it) so it can't stain until the chlorine breaks down the sequestrant and off you go again on the spend cycle. Sequestrant also uses up chlorine a bit quicker in order to break it down so financially a double whammy.
Better to find the source and stop it, then remove the iron from the water permanently.

[Denniswiseman]

Hi Dennis, who's glass media are you using for filtration?
AA treatment just changes the form of the iron from Fe3+ to Fe2+ it just get re oxidised back to Fe3+ with the addition of an oxidiser like chlorine. Sequestrant just chelates it (binds it) so it can't stain until the chlorine breaks down the sequestrant and off you go again on the spend cycle. Sequestrant also uses up chlorine a bit quicker in order to break it down so financially a double whammy.
Better to find the source and stop it, then remove the iron from the water permanently.

No Idea who's glass and where the iron came from as I don't have iron in my system and the only other way is to do a water change and with it floating out before am reluctant to do so
The only other way is to get a large enough tarpaulin or plastic over the pool and start filling it whilst draining down thus keeping the two waters separate ( I would need it 8m x 10m )

[Teapot]

Contrary to popular (pool industry) beliefs you can remove the iron. The glass media is a bit of a plus, although more so if it's Dryden Aqua AFM. Worth taking a look at the glass. Very regular grains like granulated sugar in green and brown glass and it could be AFM, this glass media is treated and has a higher attraction level for iron.

[Denniswiseman]

Would backwashing remove it from the glass media or is there another process