Basement Drainage Sump Calculation

Rain fall totals are in linear measure per minute.

You need to know the maximum flow from your sprinkler system. Which will be GPM over the area of your floor. Convert the volume to inch³ or mm³ and divide it by the area of your floor. Use this figure as you did rain fall totals.

For maximum flow from you sprinkler system I would use the figure which would represent a busted main line.

I did this calculation in Metric

Based on Rainfall Calculation.

As per 50mm/hr Rain fall calculation i had got the answer in LPS/M² and based on this i consider if total basement area is 7000 sqmtr and we proposed only 1 sump in the center of this area (considering the colume footing and parking layout) and the drain channel what we proposed is not more then 450mm deep at any point. size of the drain channel is 250mm wide and 150mm starting depth slope 1:300. Proposed sump size is 2 x 2 x 1.5 M deep.

and the answer we get, our submersible drainage sump pump capacity is 43 LPS. with (1w + 1s) and at the peak load both are working.

Is this the right calculation.

Based on Sprinkler Calculation.

I had tried to calculate this, as per AMAO area is 360m² , so total sprinkler will be install in one AMAO are 30 Nos., K factor is 80 +-5, so total discharge from one AMAO sprinkler is 2400 LPM, at the maximum total 3 AMAO can be activ at one time. so total discharge is 2400 x 3 = 7200 LPM OR 120 LPS. considering this calculation for the same basement area 7000 m2 in 1 drainage sump, the pump capacity will be 60 LPS with (1w + 1s) and the peak load both are working.

Is this the right calculation as you discribe.

Thanks,

Assuming that your basement is covered, you should not get 50mm/hr into your basement (at least when all construction is finished). The 43 lps would be during construction, when basement is open to elements and should be the responsibility of the contractor to deal with. After construction, confirm that the roof drainage is sufficient to drain the water from the building without pumping.

Water does get into basement from ground water seepage thru walls, floor, and drain pipes. Find out from the structural/foundation designer what the soils condition and expected ground water table elevations. Ask what type and size of footing drainage will be provided and expected water flows. Ask what type of basement floor and wall waterproofing is specified, and what the permeability numbers are for the selected systems. From these numbers you can begin to estimate normal ground water flow rates into the basement.

For the assumption of 3 sprinkler heads, your proposed method to determine flow rate seems reasonable. As previously noted you might want to consider the risk of flow from a broken fire main, and determine if that should be the criteria to develop the sump pump size.

You may also want to consider using multiple pumps for redundancy and low flow economical operation. Three 50% pumps will reduce electrical demands and provide redundancy and backup capability.

Thanks Ride now i got the right answer. It was nice to talk with you, thanks again.

Vj Saini

Ozzb, Ried

Thanks to both of you for suporting me,

and thanks to Global Spec The Mechanical Engineering Section.

Regards,

Why waste your time? You will end up with an expensive oversized pump that will probablly fail prematurley due to it being oversized and constantly starting and stopping. Calculate the rate for average rainfall and either pray your house doesnt catch fire (if it does the pump size wont help) or insure it.

Good point. Thanks for the touch of sanity.

Install the sprinkler system properly so it does not break or get damaged, and the sump pump does not need to handle sprinkler system flow. Size the sump pump for the expected seepage through the floor, walls, and joints.

Better yet, why have a basement at all?