Flow rate through passive main drain?

[tomfrh]

I have a single skimmer with a passive line to the main drain.

What sort of flow rate do you get through the passive line compared to the amount coming in via the skimmer? Is it substantial? Does it aid circulation?

I ask as were replastering the pool and I can either use a suction cover on the main drain, or a prettier hidden cover, which won’t allow any suction. If I did that I’d plug the passive line…

 

[Jimrahbe]

Tom,

Main drains are not really needed in most cases.. I have two rent house pools that have no operating main drains and they work just fine.

When the main drain is plumbed into the bottom of the skimmer, then (in the US) you need a floating diverter to make the main drain work. I assume this is what you mean by "passive".

Neither of my rent house pools have a diverter in place.

Thanks,

Jim R.

 

[tomfrh]

Yes by passive I mean the main drain is connected to the skimmer box. The port is just above the skimmer basket.

I was under the impression that the port provides some suction effect even without the diverter in place? I presumed some of the flow is coming from the skimmer opening and a smaller amount from the main drain line.

Is this incorrect? If there is no flow thru the main drain line in normal operation then I’ll happily omit it and put a pebble cover over the main drain opening.

 

[Jimrahbe]

Tom,

I suspect that our skimmers may be different that yours...

Over here, skimmers have two pipes in the bottom under the skimmers basket.. One is the suction line going back to the pump and the other is connected to the main drain.. (or capped off)

The only opening above the basket is a small hole, about 1" or so, that is used as an overflow or fill line.

Without a floating diverter the main drain will never work...

Posts some pics of what you have and it might ring some bells with some of our other members..

Thanks,

Jim R.

 

[wireform]

I wonder if what he describes isn't an overflow and the skimmer pipe is joined somewhere else with the MD. Can you send pictures of the equipment pad from various angles so we can see what you have.

 

[tomfrh]

I wonder if what he describes isn't an overflow and the skimmer pipe is joined somewhere else with the MD. Can you send pictures of the equipment pad from various angles so we can see what you have.

see pic

that hole is 40mm pipe and connects directly to the main drain.

it is directly above the skimmer basket and is normally submerged. The pool is currently empty.

 

[Jimrahbe]

Tom,

Thanks for the pic...

I can't see how that pipe would have any appreciable flow from the main drain... I guess there might be a very small amount of flow caused by the water flowing down and back to the pump, but it can't be much.

Here, one of the main reason for a main drain is.. if your water level drops below the skimmer mouth the main drain can feed the pump.. This assumes there is a floating diverter installed under the skimmer basket... That obviously can't happen with your set up.

Thanks,

Jim R.

 

[tomfrh]

I think I’ll just plug the line with an expansion plug, and put one of these covers over the main drain and hydrostatic valve

MAIN DRAIN - RETRO-FIT LID KIT

The AQUEA Retro-fit Lid Kit is the perfect solution for upgrading many popular main drain fittings during pool renovations or refinishing.The flush-fitting lid integrates into the surrounding pool interior for a flawless finish every time, and the 'twist and click' lid avoids fiddly & unsightly...

www.aquea.com.au