Thread: Drainage Pump

Originally Posted by echnidna

The Victorian house I'm renovating was only built a few inches above the ground. Over the last 100 or so years the ground surrounding it has been built up by about a foot so the house now sits very close to the ground in a hollow.

There is no way I can use cutoff drains to keep the ground under the house from flooding in extreme rains as there is nowhere I can gravity drain the water to.

However if I feed the cutoff drains into a pit I could pump the water away.

So what type/make pump and float switch should I use?

Yarhh, what about a bilge pump from a boat matey?

Al

Bob,
I can well relate to your situation.
The EXTERNAL laundry floor WAS about 150mm (6") lower than the nearby Lawn.
Also the Lightbulb was ONLY about 6'2" off the Floor................
I'm 195cm (6' 5" ish)
stood up into it one day,
Immediatly sat on my Rear:eek: :mad: :eek:

THAT Laundry nolonger exists.

My Garage is the opposite.
Previous owner(s) kept topping up the DIRT floor with Bluemetal.
Started pushing the Walls; and timber stumps, out.

I've used Grundfos for Yonks, they have been good for me.
A bit on the $$$$ side though.

Bob,

Pardon me if I'm telling you how to suck eggs here, (I'll get to the pump in a minute).

Firstly, do all in your power to keep the water from under the house, and if you can somehow do it, get all the water that does get in to fall to one spot!

Next, calculate somehow the maximum amount of rain that's going to fall in a given period (say one hour - you can get that fairly easily for your area from BOM, you probably want to deal with a Q10 only. That means on average it'll overflow every ten years, but the bigger the pump the more cost.

Now dig your pit and drain the under-house area into it, without even thinking about it, a 600 diameter pipe would probably do, but note that there will be no overflow, if the the thing fills up, the only place it's going to go is back under the house!

Oz is correct, marine bilge pumps are ok, but they aren't designed to pump too much grit and stuff, so go to your local rural irrigation/pump supplier and ask for a submersible pump with a built in float switch, or compare it to one with a separate one. Switches are all electric these days, so you don't necessarily have to rely on mechanical floats as such.

If you know how much volume and head you need, the pump guy will be able to recommend the right size if he's any good. Maybe you should go to a second guy just to get some confusing conflicting sizes!

A built up garden edge round the house would help too, but make sure there's enough space for sub-floor ventilation!

Cheers,

P

Hi Bob

I like Midges response. Seems to make a lot of sense to stop the water getting in, then you do not have to get rid of it. Then have back-up.

On boat bilge pumps - I have played around with boats for 40+ years. They are not a good idea for a couple of reasons:

** Most are 12 volt DC; although you can also get 24 and 30 volt units.
** Smaller ones are very ineficient if they have to pump more than 2 metres vertically, and
** They are much more expensive than plumbing/agriculture pumps.

Cheers

Graeme

Bob, while not quite the same.....
In the last house I was in the shed suffered regular flooding because it was built at the lowest point of the yard.
It had 100mm trench drain all the way around which work well for most rain. But when a tropical storm hit, it couldn't cope. The drains also clog quickly with leaves.
After getting all sorts of fancy solutions (read expensive) for the local plumbers I went with a low tech approach. A french drain.

I removed the existing drains, enlarged the trench to about 600mm x 600mm. Lined with "geo tech" material and refilled with gravel. Refit the original drain.

When it rains the drains work as normal, but if the drain over flows the gravel trench takes the excess.

Thanks Knucklehead, I thought about a soakage pit and might go with that idea as I could upgrade to pump easy enough. And I have lots of rocks, brickbats etc to fill a trench or pit with.

Need to get rid of the Willow tree though.

Just something to watch, termites love the almost constant moisture around rubble pits and french drains etc.
Termites are very active in my area and is one of the reasons that I try and only have the overflow go into the french drain.

Termites aren't a problem at this house.