Why Basements Don’t Flood: How Sump Pumps Work



Ever wonder how we manage to build basements that don’t constantly flood out if water (almost) always flows to lower ground?

It’s not that they don’t take on water – they do. It’s that they’re designed to push out the water as fast as it comes in.

Enter sump pumps

Sump pumps are specialty pieces of equipment put in place to make sure your basements don’t flood. Water that enters the substructure collects in (sump) pits where its siphoned by the pumps and ejected outside of the building.

They’re designed at a capacity to match the amount of water you’d expect to enter the space. But, with climate change being what it is, recent weather hasn’t been playing by the rules.


Between Ondoy (international name Ketsana,) and the succeeding Habagat rains, pretty much the entirety of Manila was submerged in flood. Even houses LVLP has built in the exclusive enclaves of Makati weren’t spared from having their basements flooded out.


Basement flooding is typically a symptom of one or a combination of the following root problems –

  1. Water comes in faster than it can be pumped out. Rain can drop especially heavy or flood rises high above street level, cascading into your basement. The pump loses by sheer volume and can’t cope with the influx.
  2. It’s been raining for too long and the pump isn’t able to handle the extended use. Depending on the model or supplier, some sump pumps are actually designed to run continuously. Domestic pumps however may only be designed to run up to 5 hours in a day. Longer than that, end they might breakdown, leaving you nothing to keep your basement dry.
  3. There’s nowhere to eject water to. Sump pumps work on the principle that it takes water from the basement and pushes it out somewhere else. This would normally be the storm sewer which which also has a limited capacity,and has a tendency to be clogged with detritus and trash (read- fatburgs [LINK]). With nowhere to eject to – the system chokes and the basement floods.
  4.  Surprise, your sump pump is broken! As with all equipment it’s imperative that your equipment is maintained and is in good working order. Sump pits and pumps tend to accumulate dirt and debris, and its essential that its cleaned regularly. Different types of pumps will also have different life spans. Some domestic models have a lifespan of just 10 years. It will be good to know. Its best that you replace it early, than when it’s too late.

Worry vs Value

There’s nothing like a flooding mansion to make you ask if you should even be designing basements at all. (I mean, if even the most money-backed houses that can afford the necessary equipment suffered the inundation, what more houses of a moderate budget?)

Given the cost of land though, sometimes its something you have to do to get your money’s worth, while also meeting the client’s program. What’s important regardless of budget is that your basement treated right, having learned lessons from the disasters we couldn’t have predicted previously. (Escalating acts-of-god notwithstanding.)



Pumping flood water out aside, its also important that certain design details are kept to make sure you’re minimizing water entry to your substructure in general. If sump pumps are the sailor assigned to bail water out of a filling boat, these mitigating details make sure your vessel is taking on a little water as possible to begin with. We’ll cover these details next week, so be sure to check in again then.


Quick Questions, or have a basement flood story you’d like to share?
Email homebydesignph@outlook.com or leave a comment.

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Jiddu Bulatao

Tempered Glass Best Practices

19 Temper 3

You know what tempered glass is, and where it should be used  around your house. But should doesn’t necessarily mean that it will. Construction is complicated, and to some people, codes are suggestions more than rules.

Best practices exist to make sure things are done right the first time. They’ll also help make sure you’re getting your money’s worth for where you’re investing on your family’s safety.

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