Did a backflush, now sand filter is slowly bleeding sand into pool

[PhilTX]

I performed a backflush two weeks ago. Ever since small amounts of sand float into the pool and spa. Spa seems to get more than the pool.

Is it possible one of my laterals broke when I backflushed?

I don't want to empty my filter of sand if it could be the valve at the top causing my problems.

Where and how should I start troubleshooting this?

It's a hayward S310T sand filter (pictured below). I believe it is the original filter installed with the pool like 15 years ago. Unsure if the valve at the top has ever been replaced - I do know that some air appears to get sucked in by the valve when the pump first starts.

 

[Texas Splash]

Hey Phil! We should be able to rule out the multiport valve and spider gasket since sand shouldn't be getting up to that point anyways. The only other thought would be if there was too much sand added before or the pump was too strong, but you would've had problems before. So I suspect sand entering the pool is a sign of a damaged lateral or perhaps the center standoff pipe. With a filter that old, and the fact you are noticing some air seepage at the top, you might consider replacing the spider gasket anyways when going into the filter. Knock it all out at once. Before doing so however, check your model number parts diagram. Some MPVs you can replace just the gasket, others it's the whole assembly. Best to know before going in to it.

All of this of course is assuming it is indeed sand you are finding and nothing something else. You should be able to capture some of it to see if it feels gritty. Maybe place a sock/nylon over a return jet to make sure.

 

[JamesW]

Did the valve ever get moved while the pump was on?

 

[PhilTX]

@Texas Splash:
I had the sand replaced two years ago and this is the first time anything has happened. It is definitely sand (so gritty it broke the belts twice on my now retired Polaris 360). I'm assuming replacing anything on the inside means *all* the sand must be removed again? If so, how do I get all that sand out of that filter (I mean I used to clean my fishtank with basic suction - that work for sand also?)?

@JamesW The valve has never been moved while the pump was on in the two+ years I've owned the pool.

My filter is the one thing I've studied the least since I've had no issues (rebuilt my primary pump, replaced a check valve, fixed my control panel - so I know all the stuff that can go wrong with those). I guess I don't understand how something would break like that. Purely age perhaps?

From what I can see on various parts lists, a new complete lateral assembly with center tube is $90. Replacing the entire top valve looks to be $150. Both reasonable prices to me. Then I need the sand and gravel which I am assuming something I would need to get from a pool store and not my local big box home improvement store?