How to measure sand that is still in filter

I have read Ben talking about blowing sand out during backwashing, and that you can throttle an oversized pump down with a valve, which I have done. My question is how can someone tell if they need to add more sand to their filter? When you fill your sand filter with new sand, you put in "so many" pounds, whatever it takes, but if you don't note the level on the inside of the filter, you have no way of knowing how much you are losing. My filter's owners manual does not describe a certain level or measurement from the inside of the filter. This question is certainly filter specific, and if I need to I can post my filter's info, but is there some description out there for an internal measurement of sand? Thanks.

Sand filters come in two flavors -- top mount and side mount.
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Side mount: https://i.imgur.com/Xol0WIe.jpg

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Top mount: https://i.imgur.com/wV5uRhU.jpg

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With top mount filters, the only easy way is to use the DE test: http://pool9.net/de-test/

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So if it holds DE, it doesn't matter how much sand is in the filter? I already use DE in mine. I have the issue with too big of a pump with too small of a filter, but have learned to compensate with a throttle valve and DE.

BTW, I cannot access this forum from my home computer, says the administrator has blocked my address.

If it holds DE, the filter is functioning. It may not be optimal, but it's still working.

Regarding the oversize pump, it's a bit of a chore, but with many IN-GROUND pumps (Hayward, Jandy, Pentair) you can replace the original impeller with one that's a step or two down. This will cause the pump to draw less electricity and pump less water. It's not quite optimal, but it's close.

HOWEVER, you have to replace the impeller and pump seal, and possibly the diffuser. Also, on many pumps you'll need to replace the case seals. It's not super hard, but it's not for beginning DIY'rs. One important tip: many screw-on impellers are reverse threaded!

Regarding the block: when I became active on the forum again this spring, I had accumulated over 10,000 spammer registrations AND had 3,000+ spam posts in the moderation queue -- most of them porn.

Right now, I'm using brute force methods to keep them out, including blocking IP ranges that include proxies or spam sources. For example, because both Caltech and MIT host "Tor" routers, I've blocked their entire networks (or at least all I could find) . . . and I won't lower those blocks, until I have a more sophisticated firewall in place that can dynamically block anonymous proxies and VPNs.

But, I have made some errors. If you want to check, go to "whatismyip.com" from work, and then email me (poolforum@gmail.com) the IP number it reports. If it's blocked in error, I'll take it down.

I have toyed with the idea of putting in a smaller impeller, but there is one nice thing about having an oversized pump. I can run an auto pool vac and a solar heater at the same time with the throttle valve wide open. This combination of suction and return restriction keeps the flow down where I like it so that even though the valve is fully open, I am not blowing fine particles through my filter(ish). I am sure its not so good on the pump, nor the electric bill, but I justify it because our electricity is so cheap here, lots of hydroelectric dams.

I will check on the IP address thing. Thanks.