Pump inlet minimum straight length.

[czb182]

Regarding the earlier recommendation of having a three way valve on pump outlet did waste. I’m looking at my Jandy cv460 and I see a 2” drain outlet at bottom. I’m guessing I can just use this instead? I haven’t checked whether it bypasses filter or not, hopefully so.

regarding check valves , apparently Jandy recommendeds 16” of head to keep it well sealed. That’s not gonna happen , but I will ask PB if they can move it as low as possible on the vertical pipe, although I guess they would need 4 instead of 1 which maybe they wouldn’t be so happy about. That would also reduce head loss in some scenarios I think because if lower flower rates on individual pipes

I put a 90 degree check valve on heater outlet going to swcg, per Jandy versus plumb template. Seems like it would actually be better to have sweep on outlet with a straight check valve.

 

[JamesW]

If you put the check valve after the pump, it will work better than keeping it on the suction.

When the pump is off, the static drop will keep it closed.

 

[czb182]

regarding turbulence on water going to pump inlet. You mentioned lower speed of water to reduce turbulence. I’m wondering if this really only matters for short pipe leading to pump. Like if whole run was 2”, if the pipe expanded to 2.5” in foot before pump, is that all that matters? The thinking is that velocity should immediately slow in larger pipe.

 

[JamesW]

What will the maximum velocity be?

 

[czb182]

I’m really thinking I’m theory. If the idea is to reduce turbulence going into pump, by lowering velocity, it should just matter size of pipe immediately before pump

 

[JamesW]

I’m really thinking I’m theory. If the idea is to reduce turbulence going into pump, by lowering velocity, it should just matter size of pipe immediately before pump

That makes sense.

As long as the velocity is below 6 feet per second going into the pump, you should be fine.

However, the velocity should be below 6 feet per second everywhere in the suction plumbing.

Using sweep elbows helps, and using straight pipe before the pump helps a little bit, but I would not worry too much about the straight pipe requirement if it took any significant effort.

Lower velocity and turbulence also help reduce the noise of water flowing through the pipes.

 

[czb182]

I’m still waiting on my PB if they will move check valve after pump, but now I’m thinking maybe I can just remove it all together. I already have a check valve after heater before chlorinator. I think that should stop all flow backwards right? If I opened pump basket it would drain suction line, but should hold up to pump outlet. If i am opening filter , then I would have already drained it. Unless I am wrong, I don’t see the point of the pump outlet check valve if I already have one further downstream.

 

[JamesW]

I would remove the check valve and install a Neverlube valve in the same body.

Do not cross thread the screws when reinstalling them.

That way, you can close the valve when you open the pump.

 

[czb182]

Yeah, I think that’s better. Would be 1 foot head less at 80gpm than check valve and less worry about debris sticking check valve. If the Jandy 3 way didn’t have stop tabs , I could have just spun it to block inlet and not need 2 way

 

[JamesW]

Take the handle off and cut the part that hits the stops.

 

[czb182]

I found you actually dont need the cut the stops. You can just remove lock, lift up on handle a little bit and rotate past stops.

 

[czb182]

Also, earlier in this thread was link to jandy valves head loss. I got another document directly from jandy, thought i would add. One interesting thing i've noticed is that it always seems be better to connect on inside rather(like 2" pipe on a 2-2.5" valve) than outside as it gives better flow characteristics. I would have expected the opposite.

 

[JamesW]

One interesting thing i've noticed is that it always seems be better to connect on inside rather(like 2" pipe on a 2-2.5" valve) than outside as it gives better flow characteristics.

It's counterintuitive, but it makes sense when you look at just the additional head loss due to the valve.

Plumbed to the outside, the water has to hit the inner lip and then go through more valve than plumbed to the inside.

On the inside the water travels through only the center of the valve between the two pipes.

It's still better overall to use larger pipe.

 

[czb182]

Thought I would follow up with relevant info talking about head loss. Opened pool up. Have vacuum and pressure gauge on pump. Measured 58 ft head at max rpm 3450, giving me 114 GPM, pretty nice! That’s in pool mode with spillover from spa. In spa only mode have 68 ft head for 100 GPM at max rpm. Pool only 11k gallons so I can filter through all pool water in under 2 hours if I wanted

 

[wireform]

Thought I would follow up with relevant info talking about head loss. Opened pool up. Have vacuum and pressure gauge on pump. Measured 58 ft head at max rpm 3450, giving me 114 GPM, pretty nice! That’s in pool mode with spillover from spa. In spa only mode have 68 ft head for 100 GPM at max rpm. Pool only 11k gallons so I can filter through all pool water in under 2 hours if I wanted

What you're really trying to say is, you'll move in 2 hours the total gallons equal to pool capacity but don't imagine that all the water goes through the filter in that time because turnover is a myth which means while some water may have been through the filter several times there's water that never made it to the filter even once.