Sand in pool after changing laterals/standpipe

[DJFIT99]

Hi all! First post here. We use the Trouble Free Pool method and our water is perfect!

Question: 33K gallon pool with sand filter both 5 years old. Hayward brand. We started getting sand in the pool so assumed it was the laterals. We emptied the filter of sand and inspected the laterals and standpipe. All seemed fine but went ahead and replaced the whole assembly. We backwashed and rinsed as instructed here on the forum on another post I saw.

Two days later sand in the pool again. I know it's sand and not algae because I put a sock over the skimmer and it gets full of sandy grit.

Any suggestions? All the gaskets looked good but we didn't microscopically inspect them.

On a side note, the pump motor seems to be going and we will be replacing the pump soon. It's a Hayward VS 2300 1.65 hp

 

[Texas Splash]

Some things that come to mind you may want to check or confirm if you've already done them:
- Was the filter partially filled with water when the new laterals were installed and before adding the new sand?
- When was the last time you opened/inspected the inside of your mulitport valve (MPV) - channels, spider gasket, etc?
- Do you always turn-off the pump before changing MPV selections?
- Do you turn the MPV in the same direction each time?
- What kind of sand are you using, and where did you get it?

Let's start there and see if we can't find you some help.

 

[Texas Splash]

Also let us know how long you are rinsing after backwash.

 

[DJFIT99]

Was the filter partially filled with water when the new laterals were installed and before adding the new sand? Yes
- When was the last time you opened/inspected the inside of your mulitport valve (MPV) - channels, spider gasket, etc? This was the first time we ever opened the MPV.
- Do you always turn-off the pump before changing MPV selections? Always.
- Do you turn the MPV in the same direction each time? Yes.
- What kind of sand are you using, and where did you get it? We bought it from the pool store that installed our pool. Pool grade sand 20 .

ETA: Rinse for at least 1 to 2 minutes. I know this is important.

Thanks for any help!

 

[Texas Splash]

Well, everything you noted seems very standard. Even the multiport valve was a stretch, but figured I'd check just to make sure. The only thing I can think of at this point is to go back in there and inspect the laterals and center pipe - both the pipes and their connections/knuckles. I'll ping @Bama Rambler just to see if we're missing anything.

 

[Bama Rambler]

We do hear of a lateral failing in service, but it's not common.
The multiport can bypass sand if the spider gasket is compromised. Did you see anything that looked suspect when you opened the valve and inspected it?
Also besides the laterals and head, the connection between the standpipe and multiport valve can leak.

 

[DJFIT99]

I will check tomorrow. It's so frustrating and I appreciate your help. Hopefully we can get it sorted out.

 

[JamesW]

Did you put a sock over the skimmer while vacuuming?

Do you have a picture of the sand that you're getting?

 

[Flying Tivo]

- When was the last time you opened/inspected the inside of your mulitport valve (MPV) - channels, spider gasket, etc? This was the first time we ever opened the MPV.

Do you mean you took the MPV apart? Like 6-7 screws and opened it? There is a gasket in there like a spider web. Is it in good shape?
You are probably referring to removing the MPV from the filter/stand pipe.

 

[DJFIT99]

We didn't take the MPV all the way apart. Will do that tonight after work. Here are two pics - one is the skimmer basket with a pantyhose over it to catch the sand. The other is inside our Dolphin Nautilus vacuum.