Another "How do I fix THIS mess?" Q - Swimming Pool Edition!

OK, I have a house which was a foreclosure and sat vacant for 2 1/2 years. Add in the neighbor’s kids who like to throw things in water, and my own (put some damned fish in it as forget it" attitude, and we have the current situation:
There is a blockage between the floor drain and the skimmer - if I lower the water level below the skimmer inlet, the pump goes almost completely dry.

What tool should I use to blow the crud out? I’m assuming that it will be a high-pressure device which can be shoved into the drain’s outlet line in the bottom of the skimmer - but what? How much pressure? (this is 1 1/2 sch 40 PVC in a gunnite pool 15,000 gal). How do I ensure the force go into the pipe and not back in my face?

At this point I’m thinking: take pipe fitting to tool rental place, try pressure washers’ nozzles on the pipe to check fit, select unit which comes closest.
Any recommendations on grates for the drain? Maybe a stainless steel colander or cooking strainer?

The tool you are looking for is a pipe jetter. It’s sort of like a pressure washer attached to a hose you snake down the pipe.

When you do this, you are going to clear out a lot of crap in the pipe. Most of this will be caught by the pump strainer, so you will have to clean the strainer frequently. And if you can bypass the flow of water from the pump discharge straight to waste, do that rather than putting the water with the crap that gets past the strainer into the filter. Otherwise you will also be backwashing the filter frequently.

Thanks for the name!
Won’t the crud be flushed into the pool water? I do want to approach this from the skimmer side, right?
What I can’t snag with the leaf skimmer will either sink or (eventually) get sucked into the pump’s skimmer, right?
The line from the skimmer to the pump is fine - it’s the one from the pool bottom into the skimmer that’s the problem.
I did shock the thing when I first moved in 3 years ago, so the circulation was working then - the clog is probably the mate of the one kid’s sock I found, or some other toy…

Hard to tell, other than to say that you’ll find out when you do it. And you’ll probably approach it from the end that is easier to access, and only try the other end when the first doesn’t work. It’s war, man!

But despite your best efforts to keep things clean, some of the debris will be dragged along into the strainer, pump, and filter because that’s the way the water flows. You’ll just need to clean it out too.

This doesn’t quite make sense to me. The main drains do not normally flow to the skimmer but to the pump and then to the filter. The skimmer also flows to the pump and then to the filter. If your clog is from the main drains to the pump, attaching some sort of power jetter/flusher to your skimmer will do nothing.

This pool is plumbed as follows:

bottom drain is connected to skimmer sump
pump inlet is connected to skimmer sump

The pump draws water from both the skimmer inlet AND the bottom drain. Remember “water seeks its own level” - both the water from the skimmer inlet and from the bottom are trying to fill the bottom of the skimmer.

The skimmer sump acts as a buffer - the pump will always have that water to keep it cool, and, should someone let the water level drop below the skimmer inlet, the water from the bottom will fill the sump, keeping the pump happy.

From what I can tell from discussions with pool people, google, etc. this is the norm for residential pools in central CA.

This skimmer sump has two pipes coming up into the bottom - onw is from the bottom drain; the other is the outlet to the pump.

Yours sounds different from every pool I’ve owned, although none ever in California.

I’ve always had lines that run from the main drain to the pump and lines that run from the bottom of the skimmers to the pump. I also have a valve that allows the pump for pull water from the main drains, the skimmers, or both. Water then flows through a removable basket for filtering out larger particles before going into the filter. After passing through the filter water flows through the chlorinator and out of the return outlets in the pool wall.

California pool owner here (not sure why we are talking about California pools, but…). In my area, pool supply stores will do a free water chemistry test if you bring them a sample. I suspect that if the pool hasn’t been drained and refilled since it was cruddy, the water chemistry may be screwed up enough that they may recommend that you drain and refill it. When it is drained, you can work on the plumbing, and might even consider having it acid washed to clean the plaster, kill embedded algae and clean the scum off the tile. A fresh fill and proper treatment and you’ll be good to go for a long time. When I had my 50 year old pool pool re-plumbed and re-plastered, we eliminated the bottom drain altogether in favor of a pool sweep. It is safer because there is no possibility of someone getting caught in the drain suction and drowning when there is no drain to suck. In both the old copper and new plastic plumbing, the suction lines were/are y’ed together through a valve that regulates how much water comes from the skimmer and how much comes through the pool vac or the old bottom drain.

Professional advice can be a good thing.

Well, I did drain and re-fill.

Could not readily find a rental jetter, so I tried a baby (1600 psi) pressure washer.
It did a wonderful job clearing the jets in the spa, and produced an impresssive flow up from the drain.
Turns out I have another dying pump - as I was adjusting valves to test from/to options (pool or spa) I found that the dry running occurred even when plenty of water was available.

(for those wondering: an in-ground pump has to be able to lift water from the pool up to itself - that energy will produce an impressive geyser if one has an upright cartridge-type filter - remove the filter cover, and the water comes straight up. A healthy pump will produce that geyser as long as it has water to pump. These motors are really 3/4 - 4 horsepower - they produce lots of heat and require cooling. Pump mfgrs are lazy and use the water in the pump to cool the motor. If a pump is run dry for more than a minute or two, the bushing/bearing will start to seize - the geyser will appear briefly, then there may be no flow at all - eventually it will seize completely and you now have a large doorstop.
This one is in that process.

RANT: any idiot should have seen the need for an automatic shutdown in the event of a loss of water pressure - any one who just flips on the pump and walks away from a crud-infested pool is risking burning up his pump if enough crud comes through to clog the pump’s strainer basket.
It has taken until now for Hayward to install a pressure switch - but you have to buy the top of their line to even get that.

Oh - plumbing:

This is a mid-80’s design pool/spa combo
There are 2 valves - one selects the water source (pool (skimmer sump) or spa drain), the other the destination.
The spa plumbing is a bit scary - there is no alternate source if you select the spa as the source, the floor drain in the spa had damned well better not get plugged - that is instant “dry pump”. With the pool, as long as the water level is above the bottom of the skimmer sump, either source (skimmer inlet or drain) can be blocked without harm.

Is there any reason to use a “pool pump” as opposed to any other type pump?
The one currently dying is not even self-priming
I may have to look into alternate pump types…