Sump pump

[baileyboy]

Hi,
I have - 6 inch fall from our backyard to the road (around 40m) and our block is extremely flat so I'm going to install ag pipes around the house to collect water at the back (where it is naturally collecting) and then a sump to pump the water onto the road.

I had a look on the net and can't find much information on sump design. Anyone has done one before and don't mind sharing?

[Danny]

What size sump (volume & dimensions) and flow rates do you think will be involved?

I feel that you might have to look at a two stage sump, the first pit would have a lower infeed orifice and the exit/overflow would be through an upper pipe. This pit would serve as a sediment trap. The second pit/sump would receive the cleaner water and this would allow you to have a submersible (dirty water) pump on a raised platform that sat just above the bottom of the sump. Good sediment traps also have baffles to reduce inflow turbulence (which promotes settling) and are easy to clean. You might be surprised at the amount of suspended solids that turbulent water can carry.

The trouble as I see it would be the volume of water you would be collecting during heavy rain. For this reason, you would need a healthy mitigation capacity unless you wanted the expense of a large and expensive pump. A float operated submersible would provide automatic operation unless the power went out and so you would also need an overflow provision.

Have you used the search facility to look for threads dealing with sumps and pits?

[shauck]

What about a "soakaway" (UK term) or infiltration system instead. No need for pumps, just holds the water in an underground porous holding tank and lets the water find it's way into the water table. Google it and you'll find many different ways it can be done from pits with rubble to more sophisitcated man made products.

[Tannwin]

No need for pumps, just holds the water in an underground porous holding tank and lets the water find it's way into the water table

This can cause untold trouble. I saw this done south of Adelaide where there is a limestone shelf a few feet down on a sloping block. The water hit the limestone then over time washed under the house, undermining the footings and the house virtually broke its back settling and massive cracking everywhere, so I wouldnt recommend it.

[shauck]

I guess you have to assess the situation well before doing so of course. Have the ground checked out. I think bailey boy is saying that it needs to be pumped up a slight incline to get from backyard to front?

[Danny]

baileyboy is in Brisbane and rubble pits / soak wells are in common use up there. The problem with their use during the continuous heavy rain over the last 15 months is that the pits and the earth have limited capacity to hold/absorb water and the rainfall during that time have seen rubble pits filling with sediment and the ground exceeding the point of viable hydraulic conductivity. This has led to massive amounts of water overflowing from one property to the next and you would not want to be the person living in the house at the bottom of the hill.

[shauck]

Yes. Getting rid of your problem and passing it on to someone else is not the solution. They would need massive pits I imagine. Not always feasible.

[Danny]

I have overlooked the fact that you might (most probably) not be allowed to use (rely on) a pump for detention drainage. You need to check the regulations in your area but you will probably find that gravity drainage must be sufficient to cope. This is not to say that you still couldn't pump it if you chose to ignore regulations. Did l just say that?

Sorry I didn't think of this earlier.

[manofaus]

I would have thought that you are only responsible for the water that falls on the roof and not on the ground. no?