Pool guy says I need to add sand to my filter because the sand dissolves over time. Is this true?

[JamesW]

Here are three lines on the filter.

The top line is the maximum fill.

The second line is the average fill and the bottom line is the minimum fill.

 

[JamesW]

https://www.pentair.com/content/dam/extranet/nam/pentair-pool/commercial/manuals/filters/triton-instructions-english-spanish-french.pdf

 

[ferretbone]

A serious company built the pool and installed the machinery. Also, I haven't had any problems for the last 12 years so probably the amount of sand was ok. This guy just stuck his hand in and said it was low. I estimate it was a little over half full. He then went on to tell me that the sand dissolves with time, which it seems is untrue.

Never heard that one before. I didn't know all these years I could have been topping off the sand filters instead of changing the sand out. Don't let him add more sand unless you have him change the old sand out first. Mixing a few bags of new sand with the old sand isn't going to improve anything.
Also the sand will feel loose and free in the middle. Down along the inside walls all the way to the bottom is where the real gunk collects.


Those Tr 100 sand filters are 600lbs. 600lbs of sand takes you to the top line just at the diffuser pipe. Thats where everyone I know fill them to. Thanks for posting those charts.

 

[JamesW]

The top black line is about where you want the sand surface to be.

 

[mobtr]

The filter is 30" in diameter, which is 4.9 square feet.

So, the backwash flow rate should be about 73.5 gpm.

I think that you might have a SW5P6RG1, which is rated at 27 cubic meters per hour (119 gpm).

Sta-Rite SW5P6R Pump (Salt water) | PENTAIR | Pompe piscine Sta-rite

The Sta-Rite SW5P6R is the best pump around if you require a very high flow rate and where extra quiet operation is required or preferred. | Sta-Rite SW5P6R ...

www.c-piscine.com

So, the pump is oversized for the filter and you could be losing sand during backwash.

View attachment 367875

Is there a way for me to check this? I may be losing sand but I may not, how do I test?

 

[mobtr]

The top black line is about where you want the sand surface to be.

View attachment 367957

Thanks for the very clear indication. That is about where he reached his hand to when he opened it, so I think the sand is fine. He also took out a handfull and it wasn't clumped or hardened. It looked fine although there were different sizes mixed together.