Plumbing Check... Pool Dig Next week.

[jedigrover]

Pool builder said we could step up to 2.5 for spa but he recommended 2.0” for skimmer and main drain which would stay on same line. Returns are smaller I believe. Is this acceptable?

I just re-read the bit about the drain and skimmer staying on the same line. Did he give you a reason? I think he’s just trying to save money.

That means that you will have a “skimmer UFO” and have to fiddle with it to balance flow between drain and skimmer. I wouldn’t want that. The 2” lines are acceptable, but I would wand separate drain and skimmer lines to the equipment pad.

 

[AQUA~HOLICS]

The dual port skimmer is designed to have the main drain plumbed directly to the front port of the skimmer, the UFO is a safety valve designed to allow the pool water be pulled from the bottom of the pool if the water level was to reach below the skimmer.
Return lines are smaller to allow for more pressure for moving water flow and direction.

 

[Myburneraccount]

I just re-read the bit about the drain and skimmer staying on the same line. Did he give you a reason? I think he’s just trying to save money.

That means that you will have a “skimmer UFO” and have to fiddle with it to balance flow between drain and skimmer. I wouldn’t want that. The 2” lines are acceptable, but I would wand separate drain and skimmer lines to the equipment pad.

He said it was for entrapment reasons as it would prevent too much suction to just the bottom drain. He showed me the UFO inside. How hard are those to use to balance the suction?

 

[AQUA~HOLICS]

When the door is fully opened it only allows water from the skimmer to the pump.
However much you open that door will allow water from the main drains (36” apart from each other) to supply water to the pump.
Most commonly the door is left completely opened so the safety valve is in operation.

 

[jedigrover]

He said it was for entrapment reasons as it would prevent too much suction to just the bottom drain. He showed me the UFO inside. How hard are those to use to balance the suction?

It all depends on code. He’s already showing dual main drains, so there is already an entrapment protection. Maybe a California thing. You almost never see the front port used here. The reason I like separated lines is for hydraulic reasons…it affords you the ability to manifold both lines to larger piping at the pad and keep the flow velocities in the pipes down. You can move more GPM at lower speeds in the piping.

The return piping should generally be 1 pipe size smaller than suction, as it will then provide the back pressure to limit the GPM that the pump can move. You always want the limitation on the discharge side, never on the intake side.

 

[Myburneraccount]

It all depends on code. He’s already showing dual main drains, so there is already an entrapment protection. Maybe a California thing. You almost never see the front port used here. The reason I like separated lines is for hydraulic reasons…it affords you the ability to manifold both lines to larger piping at the pad and keep the flow velocities in the pipes down. You can move more GPM at lower speeds in the piping.

The return piping should generally be 1 pipe size smaller than suction, as it will then provide the back pressure to limit the GPM that the pump can move. You always want the limitation on the discharge side, never on the intake side.

This makes sense. My runs will be 30-40 feet. Is 2” on a shared line too small?

 

[jedigrover]

This makes sense. My runs will be 30-40 feet. Is 2” on a shared line too small?

It all depends on the designed flow rates.

Generally, they should start from the volume of the pool. For residential, they would then probably assume 1 turnover of the volume per 6 hrs. TFP doesn’t really subscribe to the turnovers advice for the perspective of maintaining water quality, but pool design will use a rule of thumb like that or will be required by code to meet some spec along those lines. That gives GPM (gallons per minute) to try to hit with filtration. From there, there are some standard tables to show flow velocity vs. GPM in sizes of pipe. You try to avoid going above 6 ft/sec on suction side and 8 ft/sec on discharge. That’s generally the limit. A more reasonable design goal would be to try for 4.5 ft/sec on suction side to stay safely away from starving the pump and even getting into cavitation territory. From there, you calculate total dynamic head based on pipe size, distance, fittings and restrictions, heights, etc. After knowing all that, you can look at pump curves to see what matches. Unfortunately, that last step gets the least attention. People slap a VS 3HP pump on the pool and maybe dial back the speeds. But these pumps are capable of going well beyond the design goals, which is why I advocate for adding capacity on the suction side. Build is the only chance you have to get that right.

Just make sure the builder is thinking about these things and not just winging it.

 

[vtpools]

He said it was for entrapment reasons as it would prevent too much suction to just the bottom drain.

That's silly. It's his job to size everything and install the drains so that entrapment isn't an issue. Current code (not adopted everywhere) states that equalizer lines are not to be installed on new construction. It's a dated practice and the skimmer and drain should each be run back to the pump. Additionally, you have an autofill so you shouldn't be worried about the water going below the skimmer.

 

[Myburneraccount]

That's silly. It's his job to size everything and install the drains so that entrapment isn't an issue. Current code (not adopted everywhere) states that equalizer lines are not to be installed on new construction. It's a dated practice and the skimmer and drain should each be run back to the pump. Additionally, you have an autofill so you shouldn't be worried about the water going below the skimmer.

How hard should I push for this? Can you help me understand how undesirable having the two tied to the same line is?

 

[vtpools]

I think having both on the same line is a nuisance. Much better to be able to easily isolate one or the other with a valve. Also makes winterizing easier of the lines are separate.

 

[Myburneraccount]

I think having both on the same line is a nuisance. Much better to be able to easily isolate one or the other with a valve. Also makes winterizing easier of the lines are separate.

Thank you. I will request.