New pool. Not enough suction on dedicated line?

[maxjar10]

Hi All,

Thanks again for all the help with everything everybody. We had our pool built about a month ago and I put in the Hayward Navigator Pro yesterday (been 30 days so should be ok on the quartz). Anyway, when I hooked it up to the dedicated suction port on my pool I used the provided flow gauge (which has a min/max) and was not getting enough suction to reach the minimum.

Some details:

• Intelliflo VS
• Dedicated suction line 1.5"
• MD/Skimmer are tied together 2"
• 1.5" line from equipment to pool (argh; wish I had done 2") which splits into two returns (another separate run for the waterfall which is pretty much always off)
• Runs from pool to the equipment pad are 80ft (two 90 elbows at least but probably more like 4 from equipment to pool)

So I started playing with the pump speed and the diverter valve (between dedicated suction and MD/Skimmer). The pump rpm was 1850. I pushed the valve all the way to DS and still didn't reach the minimum flow. Then I pushed the pump in increments up to 2250rpm before it finally reached the minimum mark on the flow gauge. The water in the pump filter basket dropped down to the top of the basket (decent air pocket). So my thought is either that it's creating a vacuum (cavitation?) due to insufficient ability to suck from the 1.5" line or I have a suction leak. I turned it all off quickly because I was worried about overdoing the suction. But, I'm also surprised that I need so much suction to get the flow gauge to MIN. Clog? Is the 80 ft just too far for 1.5" lines?

Thanks!

 

[mas985]

By flow gauge are you talking about the filter gauge? The max/min levels on the gauge are pretty much useless so ignore those. What is the actual filter pressure at 1850 RPM? But it sounds like you have a suction side leak that you need to find.

Also, are you trying to run just the suction port for the cleaner? That will have way too much restriction when operating at higher RPM so you just need to run fast enough for the cleaner.

 

[maxjar10]

Hey Mas,

Thanks so much for replying (I've read your other posts and know that you are the expert on all things plumbing). The flow gauge is a little gauge that came with the Hayward (Amazon.com: Hayward V574P In-Line Flow Gauge Replacement for Hayward Select Pool and Spa Cleaners: Patio, Lawn Garden) which attaches to the end of the pool cleaner hose without the cleaner and you clamp it back on the vacuum hose. I also bought a FlowVis check valve but haven't installed it yet.

I'll have to check the filter pressure when running the vacuum suction (if it's on the 2" suction line it's about 8 or 9psi). Ideally, I want to run the vacuum at the same time as skimming by putting the diverter such that I'm pulling from both. Originally, I tried doing that at 2250rpm while the spillway was on to the spa (so it was pulling from the 2" skimmer and 1.5" suction line and feeding a 2" return to the spa) but that's when I saw the cleaner gauge that hayward provided was below the min. Then I diverted more and more to the 1.5" line until it was fully open which gave me minimum required flow but I saw the pump basket wasn't full and at 2250rpm. I stopped at this point and thought I should ask you guys because I don't want to do any damage to anything and was worried about trying to suck too much from the 1.5" line at that RPM.

If it was enough pressure to cause cavitation wouldn't the flow gauge show way more than min suction or is 80ft of 1.5" pipe just impractical for the cleaner?

Thanks!

 

[Jimrahbe]

If I understand correctly you have one intake valve connected to your pump's input, that lets you select between the MD/Skimmer and the Dedicated Suction (Vacuum) input. If this is true then I suggest you do the following.

1. Fully turn the valve to the MD/Skimmer position.
2. Increase the pump to 2500 RPM
3. Connect your Navigator
4. In small increments, very slowly move the valve towards the DS position, but stop when you have it set to about 75% DS and 25% MD/Skimmer.
5. Assuming the cleaner is then working , you can fine tune the valve so that you have as much water coming from the Navigator as possible without sucking the pump basket dry.

Let us know how this works..

Jim R.