Sump construction Basics
For a normal single family a 2000 litres Overhead tank lasts for 3 days to 4 days depending on how judicious your usage is.
So with lot of calculations, reading over the net I finalized that 6000 litres sump capacity is enough.
So based on available width and length in you property you need to decide what depth you need to excavate to reach 6000 litres capacity.
Here is the conversion
1 cubic feet = 28.3168 litres
6000 litres = 212 cubit feet
So let us consider that you have around 10 feet in length and 5 feet in width available. So you need around
depth = 212 cft/(10ft x 5ft) = 4.24 ft
So you can construct upto 5 ft depth so that its easy to clean the sump at frequent intervals.
I think you have enough details now to arrive at your sump dimensions.
You need to excavate around 6 inches more than the sump dimension for the sump wall.
So how do you construct the sump for best leak proof dimensions.
- Outermost layer could be a layer with 4 inch brick wall. This prevents the sump wall from expansion when its filled with water.
- Now fill the outside of this wall with excavated mud and soak in water. You need to use dhimmis and steel rods to push the mud inside and allow compaction around the sump. You can also use concrete to fill the gaps especially towards your building if you have gone too close to the foundation. This prevents any seepage to reach your building foundation.
- Now allow a day or two for the wall to set and cure it properly.
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Sump wall construction adds extra stability to the sump - Now ask the barbender to build a mat with 8mm or 10mm rods or any remaining rebars with separation of around 4 inches or 5 inches. Better to even consult your structural engineer.
- The rebars should be bent into on another toward the edges and corners.
- Now tie a wire mesh (available in local hardware shops ) to this mat. This allows to hold the plastering better. They are secured to the mat using binding wires.
- Now mix the plaster cement+river sand[m-sand] with waterproofing cement mixtures such as Fosroc or Dr Fixit LW+ which make the cement nonporous and block capillary action. They render the plaster water proof to an extent.
- Now finish the plastering for 1 or 2 inches.
- While finishing ensure that all corners, all edges of the tank are rounded instead of a 90 degree angle to each others. This reduces the pressure water exerts on the sump walls at edges and corners.
- Don’t forget to leave the top of the sump some protrustions of the rebar mat so that it can join the roof/top of the sump.
- Allow Curing of atleast 1 week. Do not fill tank with water. Curing should be done but ensure that not much water is filled because its not good to load the tank before complete curing. So incase its raining cover the sump.
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Sump RCC wall construction with mat and mesh. - After a weeks time frame you can build another mat with mesh and do centering to support the sump top/roof. Make sure to leave a opening of atleast 1.5ft to 2ft so that a person can easily get in and clean the sump.
- Note that this is filled using concrete similar to a mould. So mix with 20mm and 40mm Jalli stones and sand and cement in right proportion. [ Cement proportion a tad bit higher ].
- Once concrete is done you need to allow 10 days minimum for any roof as per standards. Do not forget to cure with water.
- After the roof sets remove the centering. Do not worry about the top of the roof. But you need to plaster the interiors of the roof by rounding the inside edges of the roof slab. So inside of the walls is completely finished and easy to clean frequently.
- Now you need to finish the opening part of the sump. Find out the floor height and pavement height if the sump is in parking area. Once you have the floor height the sump opening is to be finished at this height or a bit higher depending on where the opening is. For example in my place I finished the sump at around 1/2 feet above the pavement area since opening was in one corner and no vehicle would go over that. It feels convenient to check the sump once a while compared to one at floor height. Also when you clean the parking the waste water will not seep into the sump if placed higher than surrounding floor level.
- Now finish the opening by constructing a wall around that sump opening upto required height. Plaster the exterior and interior of this wall and place the sump chamber plate ontop of it and plaster for neat finishing.
- Your sump is ready. Before moving into the house test the sump to full capacity and monitor if any leaks or water level reduces. If you have followed the above procedure and you have a good mason then you should not face any such issues.
- Note that you can request the mason to make the inside walls smooth and not a rough plastering surface. This makes cleaning easier.
- Before moving in clean the sump by hiring professionals at around 500 to 1000 rupees depending on how dirty the sump is. They use chemicals and high pressure washer.
Well you have just read a very detailed description of sump making. Hope you enjoyed the learning. All the best. Do read our other articles and understand your home better!
Dear sir,
I am building a house in my village. The plan has been marked, the foundation will be dug to a depth of 4 feet. We have dug 2 pits, one for the sump and the other for septic tank, both are at a distance of 3 feet from the foundation, and are 4 feet apart from each other. The sump and septic tank will be built first, and then house construction will be done. Will there be a problem structurally?
Please reply.
Secure the walls of the tank for leakage and also try to compact the soil around it by dhimmis and water regularly before cover the top of the soil with pavement. Most houses can afford only that much of distance between foundation and sump/pit. 3 or 4 feet is good enough but needs to be compacted. Check with your mason/structure on how to compact the same.
Thank you so much. You have given me a lot of relief. What I forgot to mention previously is that the sump pit dimensions are 10 x 8 x8 feet, and the septic tank dimensions are 9 x 8 x 7 feet. They are deeper than the foundation by another 3 feet. Is this ok?
Normally that is the case, sumps are deeper than foundation. I would like to only comment on the gap between sump wall and foundation. Depth is not an issue, in my view. Again, my views are from a house which has RCC structure i.e the columns are starting from a depth of 6 feet. Your foundation depth would be less than sump, but the foundation depth should be based on expertise of how much height of building, number of floors and load. That your structural guy has to help you with actual depth of foundation based on building. In anycase water the area and compact soil as much as possible is a must.
Hello sir,we plan to cover our 4 inch concrete slab (which is the roof of the sump tank) with soil and grass.
Will water seep through concrete because of regular watering of grass?
Similar to the rain falling on it. No issue..cover top with some water proof paints, membranes if possible. Else If any cracks later just fill with crack repair stuff. Nothing to worry. Its all do it your self stuff.
Hello,
I am from Hyderabad . In the area where I am living in an independent house. There is no municipal water in the area till now. Recently the authorities have laid water pipes on the road which is 3 foot deep beneath the road. My house is at an height of 2.5 foot above road level.
To construct sump do I have to go required deep from the service pipe line i.e. 3 foot + 2.5 foot house basement height + depth required to store required quantity?
Thank you
Ideally not required..water is pumped at high pressure. So sump top can be higher than water supply pipe. My suggestion is to keep sump top such that rain water on the floor should not enter it easily. So a comfortable half to one feet above floor level(pavement). If your house is low lying areas where rain causes flooding u need to keep sump lid much higher. This is to prevent rain from getting into sump due to flooding.
Hi Mr. Naveen,
Could you please provide me the costing breakdown to construct a fully RCC cast underground water sump of 10,000 litres? Please provide the breakdown for earthwork, concrete, steel, labour all inclusive. Thank you.
Hi Naveen,
It was a great explaination on the sump construction process but can you please make a video explaining the same so it’s more easy to understand. I hope, manybif us would be looking the same information in video format. Thanks for your cooperation.
Regards,
Shekhar
Thank you so much.
Mine is a simple single story house, 900 square feet, using wire cut bricks, rat trap bond and filler slab roofing. The foundation is without columns, 2 feet wide and 3 feet deep, stone masonry , using random rubble and sized stone. A RCC plinth beam will be laid too.
All the best .
Dear Sir,
I own a Independent house built 10 years ago. My building is 3 feet above from the road level and I would like to construct now a sump of 4 feet depth to meet my water requirement. Is this okay to build this? Pls advice on the pros and cons.
Yes . Sir please follow advice mentioned in blog and use adequate safety methods. Also if possible consult a structural engineer.
Sir, I want to know how much big sump to be made for 6000 square feet roof.
Sir, in feet (length * width * depth ) * 28 is litre capacity. You decide how many litres based on my blog..Hope it helps
Great Blog Naveen.
I would like to ask which product of Fosroc is equivalent to Dr. Fixit LW+ ?
Do you know if FOSROC provides concrete mixed and layer based waterproofing for other parts of the building namely DPC, Columns/Beams, Roof Slab, Kitchen/Toilet Sunken area and External Plaster.
Regards
One thing I found is there are lot of similar products for same purpose. Some suiting specific needs. Right from terrace to cement mix to coatings. I recommend a search for fosroc water proof. There is a link which details all their product on their website under water proofing. Simplest I suggest is call their customer care they will assign a person who will tell you all details about their product for free. Shop guys normally may not know. Hope it helps
Sir I want to convert a well into sump.The diameter of the well is 3 feet.my question is what should the depth of the tank so that it is easy to maintain and two family can easily work.
Dear sir
We have constructed underground water sump with brick wall and plastering also done with water proofing liquid and thin mesh a month ago but we did not apply thin layer of cement paste. Is it ok to apply the cement paste at this moment. Can you please advice your valuable comment.
Finishing can be done anytime. Cement binds well on cement.
Dear Sir,
Thank you for your useful blog about Water Sump Construction.
Please advise me on few queries :-
Ours is an old house & we recently
constructed an Water Sump with Dimension :
7′ ( L) X 3’6″ (W) X 6′ (D).
Water Storage Capacity : appx. 4,000 Litres.
The Sump constructed using 6′ concrete block & plastered using mesh with smooth finish.
Sump construction completed
around Sept.15th & we applied
Dr.Fixit-DAMP GUARD on Internal
Walls on Oct.20th.
We started using the sump from
Oct.25th. So for about 40 days the
sump was Empty (without Water).
So the sump is being used for the last 14 days.
We just observed Reduction in
Water level by about 4 Inches per day.
Can you please advise :
(1) since the sump was empty for about 40 days, will the water get obsorbed in the begining ?
(2) Is it natural that water level in the sump goes down during initial days & for how long ?
(3) Please advise how to stop
water level reduction.
Awaiting for your useful advise.
Regards,
-Sudheendra
Bangalore
9845061943
Sir, I understand the concern. Good thing is you are watchful.
As a first step I suggest inspecting the inside of sump for cracks using some bright torch or light when it’s fully dry.
Now fill water for just few inches and watch for a day. This will tell if water is going down from bottom slab and it’s corners. And similarly increase levels to debug. Hope it helps.
Also check if you wait for more days do you see water level dropping by a feet?
Hope the sump curing was done well. Hope for the best.
Dear Sir, Thank you for your quick reply/advise. Will check as you advised. However, the main concern for us is that we do not have Borewell & we fully depend on Bwssb/Cauvery water which they supply once in 2 days (alternate days). Means keeping the sump empty for checking for several days might affect us with lack of water ! Anyway we need to check it.
Meantime, can please let us know whether the Reduction in water level of about 4 inches per day is Because we kept the newly constructed sump Empty for 40 days ?
And, even If I cannot find any crack/s but water still gets reduced, what is the solution. Kindly advise. Thanks.
As you see I am also a house owner. I can only suggest. A proper structural guy can advice after seeing your location. As a DIY person i suggest the following.
1. I don’t think water should reduce by 4 inches. I will try checking it in my sump and share experience.
2. One option is to make your overhead tank full and check.
3. Keeping empty part I am not sure, but I hope you had done sufficient curing after walls and plasting.
4. When you say mesh was it with rebars or just chicken mesh?
5. Are the corners of the sump rounded or squarish?
I suggest checking if problem is in cracks or find the source and then attempt a solution.
A proper structural engineer can inspect it and suggest if problem is confirmed. A decent 2k to 3k they may charge for advice. If the walls and packing are loose and there’s is a genuine curing or structure issue then Dr fixit etc will not hold up for long. Try to find the core of the issue. All the best
Dear Sir, Thanks for your detailed explanation.
Reg Reduction in water level, pls check in your sump & share the result.
Curing of walls was done for about a week.
Reg Mesh, they fixed Chicken Mesh.
Is applying Cement Paste on all the 4 walls & floor will be of use ?!
And, as the walls & floor is finished with smooth finish, will the Cement Paste gets Sticked on to it ?!
Pls advise. Thanks.
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Hi,
We have recently constructed an independent house. As there is no proper drainage system, the drainage water is being soaked into the ground and it is coming in our water sump as well. In this situation, may I know which option would be better for the sump? To have the concrete sump or get the polyethylene tanks ( ex. Sintex tanks)
Thank you.
regards,
Kishore
Sorry to hear that. My suggestion is to fix the sewage because of host of diseases it can carry. Sintex when I explored seemed to have cylinder shapes. Such shapes take lots of space than a rectangle. So dint go for that. Also I did not go because I imagined it has a life. But concrete sump is almost eternal with some minor repairable things. Anyway this is all I am aware of. A engineer consultion may help you rectify the sewage problem. All the best
I’m constructing a sump with L=7ft x B=9ft x D=10ft (17,800 ltrs appx) due to shortage of space. Is there a rule of thumbs that the depth should be only 5ft or less ? Concrete blocks will be used in the overall construction.
thanks in advance.
Nothing that I am aware of. For a single family I chose 5000 litres. But plan the load on the walls of the sump. My suggestion is always to make use of structural engineers to do their CAD stuff. Its not a big cost compared to later repairing it etc. All the best
Dear Sir ,
We want construct a sump of 12,000 ltrs. capacity using 8 inches cement blocksor 8 inches RCC wall or bricks.Which material will give better life without any cracks . What will be the cost difference .
Thank you
V.K.Ramu
Dear Sir,
Thanks in advance for your kind reply, though my queries are settled by reading above reply expect one:-
i.e. My mason advising telling that, plastering is not required below the concrete mat (Top cover sump) and telling me no body plaster it and water is not touching the cover?
Is he right, please advise me
Thanks
Sir. Better you tell them what to do. Do not discuss with them. Just tell them what to do. It’s easy to clean the sump if plastering is done. But don’t reason it with them. Just tell them to do it. That is easier.
Sir, is it necessary to have the concrete mat? Our contractor is saying he will pur big jelly for 2 ft and after that small jelly for 2 feet because it’s hard soil and its will be safe. Is it surely safe? Wall is constructed with cement blocks.
Sir, all forms are possible. People build like that. No issue. But Steel + concrete is rcc. Strongest. So mostly it’s your decision. Please read my initial blog on house construction. You have to decide and tell them. It’s your house. If you have a structural engineer hired you can have them tell these contractors. Else you have to take a call. If you have money and resources go for the most long lasting. All the best.
Can a sump be dug 6 inches from foundations?
My general views i have provided in blog. But if space is constraint i suggest hiring a structural engineer to inspect and take necessary precautions. All the best.
Dear sir, i am planning to built underground (30*50)+ ground floor(30*50)+1st floor (30*20), in this, i am planning in under ground 20*20 sump (rain harwest water tank.
thanking for your kind replay.
Hiii I would like so a sump of 9*1 1 depth 10 feet for rain water harvesting and chamber for natural filter around 3*2.5 3 feet depth for clear water to the sump can u plss let me know about the construction cost and how to go about it
Have not done that. You can search online for Eco construction people. They will know details.
I built an underground sump 12’X9’X11′ with coursed stones many years ago. It was not used for a long time. It developed cracks and was leaking like a sieve when I tried to use it recently. Your advice is the best I found to repair it. Thank you very much.
Happy that it was useful. Please do share your knowledge with others. Thank you.
Hi Naveen,
Pls advise on the below issue
My sump with 10000 lts capacity has many hairline cracks which are predominately visible.
I am planning to get these cracks covered by waterproofing agents
Or can I go for replastering the sump again, by removing the old plaster and putting the mesh and plastering on it
Which is the best solution?? Can I relay on waterproofing services or should I go for replastering the sump
Pls advise I am very confused
If you think structure is fine both options are okay. Water proofing experts consultation wont hurt. Take a call based on quote they give.
Sir,
I have a half site house plan.According to our plan two pillars is coming inside the sump tank.Is it good or not?
For sump construction – concrete vs red bricks – which one is better?
Depends on quality of bricks and work. Dont see any issue with either.
Hi, I am constructing new house with Sump tank Capacity of 14000 liters(Size: 8’X9’3″X7′) wih 6″ solid blocks. The depth of the sump is 2′ lower than the footing bed. Can the Sump wall be built along with Foundation Column. If so, may i know the precautions to ensure the Column and sump inner wall strength.
Sir, i have only told things to consider. I am not a solution provider. You will need to hire a structural engineer for your plan. I had done the same, hire a structural engineer to plan. So my advice is to hire a structural engineer. But please keep in mind points i mentioned while discussing with engineer. Thank you.
What is the cost of construction per cubic foot
Dear Naveen, I have finished the repair of my underground sump. I took some photos of the reinforcement with wire mesh and others. You may use them in this site if you want. Please send your email-id so that I can send them to you. Thank you once again.
Dear Naveen. Please advise on following.
A. How to take care of sump cover so that insects do not enter sump or fall into sump water. I see cockroaches and lizards entering sump.
B. What are your thoughts on stainless steel cover.
Can use rubber beeding all over to cover gaps between plate and floor and make it air tight. Again depends on type of plate.
Have not heard of ss plates. I think personally anything other than plastic may be okay.
Is steel in sump floor a cumpulsion ? most constractors avoid steell in floor.
Very good post!
I also found another website that might help users who are planning to build a house https://architects4design.com hope this helps your users!
Keep up the good work going!