Plumbing question

[adnedarn]

Hello all! I bought this house last July and it badly needed a new pump. I purchased a Sta-rite 3/4HP and plumbed it in. It is 1 1/2" lines to and from, one in and two out... My sand filter shows really low pressure, like 4psi and the suction on the pump is like 13 Hg. I guess I curious if I should flop the pump around maybe this u-turn is causing a lot of extra flow/head issues.
Thanks kindly for your time!
Andrew

here is what I started off with (and replaced)

And here is what I have currently installed

 

[mas985]

2 90's isn't muich for head loss. It is more likely that you have a suction side blockage somewhere. Try back flushing through the suction port in the pump basket to flush out whatever might be stuck in the pipe.

 

[adnedarn]

Hello Mark! I actually did do that back when I first installed the new pump- but I just now was doing it too... I did find that there was a lot of tiny leaves in the pump impeller area from the neighbors trees (as I was running water in there) so after cleaning that out all good I now have about 23Hg on the suction side and 5psi on the filter. I know 2 90s isn't a big deal, but I could have swore that there should be so much straight pipe between them *shrug*.
Thanks all!
Andrew

 

[mas985]

23" hg is much too high for that plumbing and pump so I still think you have an issue in the pipe somewhere. How long are your runs? What was your filter pressure with the old pump?

 

[adnedarn]

Hi again, the skimmer basket is only about 23' from the pipe coming up out of the ground in the pool room. So I would say easily under 30' of combined piping from skimmer to pump. I wish I could tell you what the pool filter pressure was with the old pump, but I cannot. I changed that before I even moved in (it was throwing sparks). And even if I did know, I doubt it would be any answer... The new pump threw the filter pressure high, so I changed the sand and the old sand for the most part was solidified... So, I guess that doesn't help us much.
Andrew

 

[adnedarn]

Whoops, I'm sorry.. the above is the suction/pressure with the sand shark plugged in... With that not plugged in and just the skimmer running the numbers are: 17Hg and 9psi.
Andrew

 

[adnedarn]

Well I was wrong... more like 32'. I took and fed through a thing with a 1" end on it... I made it from the skimmer all the way to the pump basket and that took approx 32' of line. Since I was able to get it all the way through, I feel like that verifies there is nothing major in the line blocking it (since the line is only 1.5").
Thanks,
Andrew

 

[mas985]

Ok, putting a cleaner on a suction port can cause very high suction but 17" is still a little high without a cleaner. I can see if your setup warrants the extra head loss so I have few more questions about your plumbing:

Pump Model #?

Is there only a single suction line?

How many return eyeballs/ports and what is the diameter entering the pool?

What is your filter size?

 

[adnedarn]

Thanks Mark, I appreciate you sticking with me on this
Pump model is STA-RITE #p6e6d-205l
Yes, only 1 1.5" suction line in the skimmer basket
return eyeballs: 2 (fed from a 1.5" return line)
return ports: 6 (fed from another 1.5" return line)
Filter size: Make: Triton II Model: TR-60

Thanks again,
Andrew

 

[mas985]

So just to be clear, are there two 1.5" return lines running from the equipment pad all the way to the pool?

Why are there two return lines? Do you have a spa or something else?

That could be why the return pressure is low while the suction head is high.

 

[adnedarn]

Mark, Yes 2 1.5" return lines from filter to pool. The one that goes to the eyeballs is just that. The one that goes to all the other returns goes to the pool side of the fence where 2 valves stick out of the ground. One of them turns off the other return ports and the other is a turn off for a 1.5" line that has been abandoned and capped for some reason. I have the sand shark plugged in and running so with that return line valve open, the filter reads 5psi. If I close that valve, so all the water returns through the eyes, the pressure in the filter goes up to about 9PSI. I have no idea what that other 1.5" line went to...
Thanks!
Andrew

 

[mas985]

It sounds like the problem is the way the PB designed the plumbing. With only a single suction line and dual return lines, there is an imbalance in the head loss. Normally, pumps work much better when the suction head loss is at least half of the return head loss. But in your case, the suction and return head loss is about the same and when you use the cleaner, it is more than the return head.

When using the cleaner 27" is very close to the pump cavitating. Does the pump make noise and/or draw in a lot of air when the vacuum is attached? One thing you can do is make sure the second return line is shut off when using the cleaner. Also, does the cleaner have a built in bypass valve?

 

[adnedarn]

Hi Mark. That all makes great sense when put together with the things I've been reading and trying to understand. Yes, I do get bubbles in the pump basket... I assumed it was cavitation and that's why I'm trying to figure out the high vacuum thing. I did find that it didn't do it as bad when that valve was off so that's how I ran it, although, I didn't know why. Sounds like I need to change out the skimmer (I can't even ID it to know what satellite valve to get) and plumb in a pipe to the drain and one to skimmer... Wonder how much that will cost. heh

OH, yes- there is an adjustable bypass in the part that plugs into the skimmer for adjusting the suction on the cleaner.

Thanks,

Andrew

 

[mas985]

Yes, I do get bubbles in the pump basket... I assumed it was cavitation and that's why I'm trying to figure out the high vacuum thing.

You can't actually "see" the cavitation since it occurs in the impeller. However, the air entering the pump basket is due to an air leak and an indication of high suction which can then also cause cavitation if it gets high enough. But since the suction is at most 23", the pump is probably not cavitating. Cavitation sounds like the pump is pumping gravel or stone.

 

[adnedarn]

Yes, that happens when I first bought the house and was vacuuming it... The vacuum would completely stick to the bottom and made it impossible to do. Other than that, just some bubbles.
Andrew