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How to build a cutoff drain sump pump pit?

I am planning to install approx 35 meters of aggie pipe drain with a sump pump pit for lowering the water table. The pit needs to be 1500mm deep. For the pit I am looking at installing Everhard 600 x 600 x 600d pit with three Everhard 600 x 600 x 300d riser stacked on top making the total depth 1500mm. It is unlikely that any vehicles would run over this pit. Are there any issues with the narrower pit and is there other pits in the market that does a similar job? Further what size sump pump would be required? Note no direct rain water would be collected except what is absorbed from the surface into the ground. The ground is medium dense clayey sand, so the vertical surface collection area into the scoria would be 35m long by 1 m deep one side only, the other side of the trench would be lined with polythene.

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MitchellMc

Welcome to the Bunnings Workshop community @kn_ll. It's sensational to have you join us, and many thanks for your question about installing drainage.

You might like to post a diagram of your setup so our members can better understand what you're planning. That way, they'd be better informed and able to offer great suggestions. Let me know if you need a hand uploading images.

Depending on your expectations for water collection, you could get away with a 450mm pit. We can Special order the 450mm risers for you. It sounds like you are installing the agline and pit particularly deep, to capture subsurface water as well. If you are successful in your endeavours, that could be an immense amount of water. Out of interest, why are you trying to capture the subsurface water? Is it heading into an area you don't want it to be? Remember, if this subsurface water is running from adjacent properties, it could well exceed the capabilities of your system, and I wouldn't have thought a lowering of the water table is particularly practical or possible.

I'm keen to hear more about your project, especially the issue you are trying to resolve.

Please let me know if you have any questions.

Mitchell

kn_ll

https://www.workshop.bunnings.com.au/discussion/comment/27707#Comment_27707

Thanks @MitchellMc

Very rough sketch below. Thankyou for advising the Everhard 450 series (450 pit plus three risers) would be suffice for my needs. I did my own calculations on water flow as follows:

permeability of clayey soil from search of internet 5.6 x 10-6 m/s x 35 metre length x 1 metre deep = 0.0002 cu m/s = 0.196 l /s = 11.76 l /min. The pit itself would be installed such that minimal surface water/rain water would not drain into it. The surrounding ground would be graded such that surface/rain water will collect into the existing storm water system.

Bunnings pump https://www.bunnings.com.au/claytech-ecosub-7-clean-and-dirty-water-drainage-pump_p4819842 = 140 l /min should suffice - do you have further comment/recommendations?

cutoff drain.png

EricL

https://www.workshop.bunnings.com.au/discussion/comment/76445#Comment_76445

Hello @kn_ll

Your plan looks very sound, my only other recommendation is to make sure that the connection of the agi pipe to the pit is very secure. I recommend using an Everhard EasyDRAIN Pit Boss Connector in conjunction with Selleys 290ml Grey Storm Waterproof Gutter And Roof Sealant to provide a good seal for the pit boss connector. Please make sure to use screws to secure the pit boss to the pit.

In order to get a good cut on the pit, I suggest having a look at the Hole Saw Kits in the tool shop.

If you have any other questions we can help with, please let us know.

Eric

kn_ll

https://www.workshop.bunnings.com.au/discussion/comment/102144#Comment_102144

Thanks @EricL. The sealant in my case is probably not required as I require the ground water to seep into the pit and any rainwater will or should be pumped out and not increase the ground water table significantly. I have further queries - how reliable are the lower end pumps like https://www.bunnings.com.au/ozito-350w-dirty-water-submersible-water-pump_p4816179. Are there other manufacturers products similar to the Everhard pit and riser?

EricL

https://www.workshop.bunnings.com.au/discussion/comment/118077#Comment_118077

Hi @kn_ll

Between the two, the Clay Tech pumps have been around for a long time and have a very good reputation.

I'm currently not aware of any other pit that will do the same work as the Everhard pits. About the only other way to replicate the pit function is to build it out of bricks and concrete.

If you need further assistance, please let me know.

Eric

kn_ll

https://www.workshop.bunnings.com.au/discussion/comment/127389#Comment_127389

Thanks EricL

A few more queries:

With either pump how high above the base is the inlet?

With the pit cover does Everhard produce a fully covered plate like a checkered plate?

I am not planning to fit a Pit Boss Connector as there is no need for a completely sealed pit - from Everharde Installation manual it states of possible movement of the pipe - do you know of have any experience with movement?.

Everhard Installation instructions state "450 x 450 pits should no be deeper than 600mm to outlet invert" - my pump would be installed at bottom of 1500mm deep pit and I understand that "the pump can be fully submerged up to a depth of five metres for efficient water removal".

EricL

https://www.workshop.bunnings.com.au/discussion/comment/133529#Comment_133529

Hi @kn_ll

According to the Ozito brochure the minimum suction depth is 50mm the gap seems to be the same for the Clay Tech unit. However, I'll double check that for you when I get a chance. But the Clay Tech unit has one feature that the Ozito unit doesn't have and that is low level suction up to 10mm when manually operated.

To my knowledge they only do the solid checker plate cover for the 300mm pits. However, they do make a polymer cover in 450mm which would be suitable for your needs. Here is the link to the cover's technical details - 450x450 Everhard Polymer cover.

Movement occurs when water enters under the bottom of the pit. This causes the soil to soften up and "movement" occurs when the water drains away causing the pit to settle.

The outlet invert refers to the bottom of the outlet pipe and the pit must be no deeper than 600mm from this point. I'll have to doublecheck with Everhard regarding the position of your Agi pipe and how deep you plan on using it. As soon as I have more information, I'll get back to you.

Eric

kn_ll

https://www.workshop.bunnings.com.au/discussion/comment/137312#Comment_137312

Thanks @EricL

I have a further query regarding float level for on/off. Refer attached sketch (NTS) - Can the float be set such that it switches on when it reaches 300mm above water level - I don't want water siting above the sand layer, The float switch turn off when its below 100mm. If the float is difficult to set then what is the minimum depth where it turn on? Further its noted that the minimum area is 500x500mm. Is this a concern if it's installed in a 450 x 450mm pit? sump pit levels.png

EricL

https://www.workshop.bunnings.com.au/discussion/comment/139925#Comment_139925

Hello @kn_ll

My apologies for the late reply, I spoke to Everhard's technical team about the proposed depth of the pit. I explained to them what you were planning, and they mentioned that they can't predict what will happen or how the pit will behave when it is buried that deep. Their warranty only covers the pit and the first riser at standard depth, any deeper than that or any additional risers will void the warranty of the product.

In regards to activation, I'm afraid you'll need to tie a rope to the float switch to manually activate it if you want the water to be less than 100mm. The float switch is sealed and can't be adjusted, so when the tank reaches 100mm it will stop pumping and when it goes above 100mm it will start pumping.

Now that I've had time to think of it, the narrow shape of the pit might not be ideal for the pump to operate in. It is clearly stated that an area of 500mm x 500mm must be provided for the pump to operate properly. If the float switch should get caught up in the corner of the plastic pit, it will burn the motor out.

As a possible alternative, I propose building the pit out of bricks, rendering it and then covering the surface with Gripset Betta 1L Waterproofing Membrane Bitumen Rubber.

If you have any other questions we can help with, please let us know.

Eric

kn_ll

https://www.workshop.bunnings.com.au/discussion/comment/141730#Comment_141730

Thanks @EricL

Everhard's comment "can't predict what will happen or how the pit will behave when it is buried that deep" is noted, However I am still planning to install the 450 series pit as the pit would not be installed at a location where there would be vehicular traffic. Only the occasional foot traffic. As for pit width, there is the https://www.bunnings.com.au/karcher-sp7-inox-dirty-water-submersible-pump_p0134552 with an internal float. Do you have any issues with this type of float?

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/143099#Comment_143099

That Karcher looks like it would be more suited to the job @kn_ll. However, these submersible pumps are designed to move a body of water; they're not designed to be permanently installed in a pit and pump water from it in rain events. That would be a sump pump similar to the Ozito 500W Vortex Submersible Sump Pump. Although they appear to be very similar in nature, typically, a submersible pump is used when no damage can occur if it stops functioning, like draining a pool. Whereas a sump pump is designed to a higher standard and is something you really need to rely on as if it fails an area can be flooded.

Mitchell

kn_ll

https://www.workshop.bunnings.com.au/discussion/comment/144057#Comment_144057

Thanks @MitchellMc

I am still planning this project and I have further queries:
Please confirm I have specified the correct parts and advise if any part missing? In particular is the check valve a special order. Are all fittings require a socket.

For the pit riser can I drill 32mm holes in the wall anywhere? In particular how far from the top?

holman 32mm pipe accsories.png

EricL

https://www.workshop.bunnings.com.au/discussion/comment/144790#Comment_144790

Hello @kn_ll

In order to avoid a bottle neck in the check valve, I suggest reducing the entire run to 25mm. This will make it easier to join the parts together and you won't have to special order a 32mm check valve.

Here is the proposed parts list:

If you have any other questions we can help with, please let us know.

Eric

kn_ll

https://www.workshop.bunnings.com.au/discussion/comment/145343#Comment_145343

Thanks @EricL

I would like to stay with 32mm as it less strain on the pump motor therefore increasing it life. Do Bunnings have a 32mm check valve?

EricL

https://www.workshop.bunnings.com.au/discussion/comment/145774#Comment_145774

Hi @kn_ll

I'll have to double check if the check valve comes in 32mm. However, as another option you could use a 40mm check valve and use reducers at the ends so that they fit 32mm pipes. As soon as I have more information, I'll let you know.

Thanks for your patience.

Eric

EricL

https://www.workshop.bunnings.com.au/discussion/comment/145774#Comment_145774

Hello @kn_ll

I've just been in contact with our provider and they have informed me that they don't have a 32mm PVC In-Line Spring Check Valve. There is the 25mm and then the 40mm. I'm going to stay with my original recommendation of using a 40mm check valve instead of a 25mm so that you don't get a bottle neck in the flow of water.

If you need further assistance, please let us know.

Eric

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