Sand in pool after backwash/rinse

[wizzardz]

Any feedback on if the above equipment is appropriately matched?

[PoolDoc]

In theory, that filter and pump are well matched. Unfortunately, most pool manufacturers tend to oversize pumps and undersize filters. Even though filters are rated higher than 15 gpm/sft, flows over that amount can wash sand out during backwash.

Your S244T filter has 3.14 sft, so it's 15 gpm/sft flow is only 47 GPM.

The SP3007x10 AZ will generate 45 gpm against 60' (or 26 psi) of dynamic head. Depending on your pools layout on the suction side, the dynamic head on simple pool is likely less that that, meaning the flow rate will be higher. One way to get an idea, is to look at the filter gauge when the filter is CLEAN. If it's less than 15 psi, your system is almost certainly running at more than 47 GPM, possibly a lot more.

Add to that the fact that the resistance to flow during backwash is likely lower than during normal operation . . . and there's a good chance you will lose sand during each backwash until the sand level is below standard.

As mentioned before, pictures would help us determine what a good solution for you might be.

[wizzardz]

Below are links to pics. I noticed the gauge is currently reading lower than when I replaced it (was about 15)






Let me know if there are other pics that would be helpful. Your feedback has been most helpful and makes sense.

I believe the psi change I mentioned above may have been before (15) and after (12) the backwash/rinse cycles.

From your description, its sounds I need a way to reduce the GPM rate. Any suggestions on how that may be accomplished? I'm guessing since the old gasket was partially blown out, it was reducing the flow by bypassing some to waste or recirc. (or the higher rate helped blow out the gasket)

thanks again

[wizzardz]

Decided to pull the top off the filter and check the laterals/sand/etc since the pool refused to clear up. Valve assembly pretty much lifted out easy enough...almost too easy.



Besides the tube being broken, I pulled the rest of the old laterals and they were just crusted over and one was missing. Fortunately I had decided to get new laterals and sand. The filter is draining very slowly so I'll have to wait overnight before I start pulling the old sand.

Whats the best couplings to use on the PVC to allow easy disconnections in the future?

[CarlD]

I like to use quick connect unions or union ball-valves if I need to isolate it. So my low-drain and skimmer have union ball valves. But between my pump and filter is just unions, and between the filter and the salt cell are unions. Between the cell and the return is a union ball valve. And so on...

[PoolDoc]

Carl's right -- I'm working on a HOW-TO on that topic for you.

Meanwhile, this detail from the picture above answers the, "what's happended to my sand?" question, and perfectly illustrates what happens when pool dudes over-size pumps and under-size filters:

[CarlD]

Yipes! That's about 10x as much as you should see!

Since I have an AG, I pull ALL the plumbing off to close and the way to do that is have quick-connect unions everywhere. Also, to isolate a section without having to plug returns, drains and the skimmer, ball valve unions make it faster and easier, say, for example, when you need to clean the pump's strainer basket, or clear SWCG protective screen. Or pull out your multi-valve!

[dcarlton]

Was going to chime in as this was actually the same problem I had today. Was getting sand in the pool after replacing XL valve and it working great for 12 hours. Went to backwash and really had no backwash pressure and really no rinse AND it was leaking out the waste port.

Thought is was the spider gasket (no), then a broken lateral (no) but like you discovered my pipe snapped at the lateral assembly. Replaced and back in business for now.