New filter, pump not drawing water

[7jx7]

Did a search, didn't find what I need. New 300 lb sand filter and pump for inground pool. 1 skimmer and 1 main drain. Only the line from main drain has a shutoff valve. Filled filter halfway with water, put sand in. Mounted multiport and plumbed new lines. Primed and turned on pump, it's working, but not drawing water into the pump. Tried both with both lines open, and then with main drain shut. Snaked the skimmer pipe for good measure, still nothing. Should I have filled the filter 100% with water? Not sure what else could be going on. All plugs, o-rings etc. Are in place. I don't seem to have an air release on this filter either. And of course in my rush, I didn't use the slip joint couplings so I'll be cutting pipe if I undo thr multiport.
Any ideas are appreciated. Some pics attached for reference.

 

[7jx7]

Update: I cut the pipes, took the multiport off, filled with water and added a few slip joint fittings. The filter was about 3/4 full of water already, so I don't think that's the issue. I'll wait a bit to let the glue cure up, but I don't think the water level in the filter is the issue.

 

[HermanTX]

Did a search, didn't find what I need. New 300 lb sand filter and pump for inground pool. 1 skimmer and 1 main drain. Only the line from main drain has a shutoff valve. Filled filter halfway with water, put sand in. Mounted multiport and plumbed new lines. Primed and turned on pump, it's working, but not drawing water into the pump. Tried both with both lines open, and then with main drain shut. Snaked the skimmer pipe for good measure, still nothing. Should I have filled the filter 100% with water? Not sure what else could be going on. All plugs, o-rings etc. Are in place. I don't seem to have an air release on this filter either. And of course in my rush, I didn't use the slip joint couplings so I'll be cutting pipe if I undo thr multiport.
Any ideas are appreciated. Some pics attached for reference.

So the issue is that the pump will not hold prime. Is the new pump significantly different from the original one?
Have you considered a check valve before the pump - on the line after the main drain tees in - to hold water in pump?
Is the new pump at the same level or higher then the pool water?

You could put a hose connection into that suction line and push water into the pump until it fully primes both the skimmer and main drains.

If the pump primes it will fill the filter so having your filter half full or even empty would not make a difference.

 

[7jx7]

So the issue is that the pump will not hold prime. Is the new pump significantly different from the original one?
Have you considered a check valve before the pump - on the line after the main drain tees in - to hold water in pump?
Is the new pump at the same level or higher then the pool water?

You could put a hose connection into that suction line and push water into the pump until it fully primes both the skimmer and main drains.

If the pump primes it will fill the filter so having your filter half full or even empty would not make a difference.

Yeah, the pump is basically the same, just a different brand (equivalent to the hayward superpump). Pump is also at the same exact level.
I threw a garden hose into the pump basket and set to recirculate and i could hear water in the return pipe from the multiport. I aslo set it to backwash...and it backwashed as well as it could with the hose flow rate, so pump and filter seem good to go. Check valve is a good idea though. I may add that.
For some reason, it's just not pulling water into the pump from the lines. I could have a clogged skimmer line since it was open without a basket for a year, but that doesn't make sense since I opened the drain line and it still didn't pull water. The pool hasn't lost any water at all in 3 days, so I don't think it's a leaking line.

 

[HermanTX]

For some reason, it's just not pulling water into the pump from the lines. I could have a clogged skimmer line since it was open without a basket for a year, but that doesn't make sense since I opened the drain line and it still didn't pull water.

Good possibility. I had a skimmer line get plugged and when both main drain and skimmer open - all worked. When just main drain open for suction it also worked. However when just skimmer line open for suction then it would not pull water to pump. But you are having issues with both skimmer and main drain drawing suction as I understand it. You can try to surge your skimmer line by rotating your valve full open to full close while pumpe is running with your hose in it. I purchased a hose from Amazon that connected to my power washer and I pushed that down the skimmer line as far as I could with the power washer. If finally pushed enough debris close to my pump that it then broke up and came out.
I purchased this at amazon

https://www.amazon.com/gp/product/B0854D9XFG/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

 

[7jx7]

Good possibility. I had a skimmer line get plugged and when both main drain and skimmer open - all worked. When just main drain open for suction it also worked. However when just skimmer line open for suction then it would not pull water to pump. But you are having issues with both skimmer and main drain drawing suction as I understand it. You can try to surge your skimmer line by rotating your valve full open to full close while pumpe is running with your hose in it. I purchased a hose from Amazon that connected to my power washer and I pushed that down the skimmer line as far as I could with the power washer. If finally pushed enough debris close to my pump that it then broke up and came out.
I purchased this at amazon

https://www.amazon.com/gp/product/B0854D9XFG/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

Thanks. I tried something similar with air today and the mystery continues. I hooked up my large air compressor to a large conical rubber plug with the air nozzle through the center of the plug, stuck it in the skimmer and blew the skimmer line. Seems like not too much debris was in there and I had a lot of psi going through there. Blew the loosened lid off the pump. So i thought maybe it could drawing air from one of the old pvc connections, so I replaced all of the 1 1/2 pvc piping from the drain and skimmer lines going to the pump, plus the pump fittings.
So now, if I have someone hold the plug in the skimmer line and I fill the line and pump with the garden hose, it'll prime up and run on recirculate. BUT 3 things:
1. If I turn off the pump, it's the same issue when I turn back on. It just won't prime, won't suck water into the basket from the skimmer line (drain line closed)
2. I tried just slightly opening the drain valve while pump was running on skimmer only and the pump lost prime and wouldn't prime up again..even after closing the drain valve immediately. Keep in mind that when I cut off the old shut off valve on drain line, you could see that the drain line was full of water.
3. I'm getting air bubbles out of the returns even after running it for an hour to purge the line, also the pump basket isn't quite full of water to the top of the cover while running. Suction at skimmer is fine.

So I have to plug the skimmer with drain closed, fill pump until overflow, start pump and have someone immediately remove the skimmer plug for it to run. If I open the drain line at all, it loses prime. If I turn pump off, I have to repeat the process to get it started.

I'm just stumped with this one.

 

[mknauss]

What you are seeing is a classic suction side air leak. Have not read that you have checked the pump basket lid gasket, the pump drain plug gaskets, and the union at the pump inlet.

Also, try to set the MPV in recirculate or waste to see what happens.

I cannot see what brand/model the filter and MPV are, but I assume the lines are connected in the proper positions.

 

[HermanTX]

Marty makes a good point. The OP stated he had only did a pump replacement with a similar (not identical) pump and a new filter. Then suction would only hold whether it be the MD with skimmer or only Skimmer. He cannot isolate the skimmer per OP picture.

Please review this video and verify all connections on the pump suction side, the pump drain plugs and the pump basket cap are all tight and air tight. Any leak on the outlet side of pump will be a leak of water whereas on the suctionside, a leak will draw AIR into the pump thus preventing water to be sucked from the suction lines.

 

[7jx7]

Thank you both for the help on this. Some great points and I have done most of this thanks to your suggestions. I have discovered the issue.....now get ready to shake your head. As context, I bought this house about 7 years ago as a fixer upper , and as a single guy I'm always trying to save some money without buying the cheapest Crud. Since I needed a new liner, pump, filter and some other work done, Instead of replacing the seized motor on my Hayward super pump (second motor on it) I went with another brand that was cheaper. The pool contractor came to came to fix a small issue on the liner track and while we were chatting I mentioned my problem and it took him about 5 seconds to realize what it was. Although the pump that I bought was a 1.5 horsepower and says it's for both above and in ground pools apparently Although the pump that I bought was a 1.5 horsepower and says it's for both above and in ground pools apparently It's only for an inground pool when the pump sits below water level, since it is not SELF-PRIMING. New pump ordered.