Flooded basement....need reliable pump recommendations and high water alarm

[Pocster]

Are you really getting the rainwater from an area of 15m x 8m?

It’s hard to know the lay of your land . Is that area funnelling the rainwater to your sunken area and sump ?

If so - then yes add a 50mm extra outlet and seperate pump .

Before I started my build my area was exposed to rain ( I.e when just a concrete base in the ground ) . Without a pump the area would be a good few inches of water after substantial rain .

[Thorfun]

14 minutes ago, pocster said:

Are you really getting the rainwater from an area of 15m x 8m?

It’s hard to know the lay of your land . Is that area funnelling the rainwater to your sunken area and sump ?

If so - then yes add a 50mm extra outlet and seperate pump .

Before I started my build my area was exposed to rain ( I.e when just a concrete base in the ground ) . Without a pump the area would be a good few inches of water after substantial rain .

here's a couple of diagrams for you.

 

 

 

the entire plot has the layer of sandstone and you can see that everything is flowing north to south downhill.

 

in the first image I've added where we've cut through the sandstone so along the 15m length of the north side of the basement there would be water coming out of the sandstone and down to the land drain and who's to say that along both sides of the house (8m in length) water isn't coming out through the sandstone there as well as it's probably a path of least resistance. so, my theory is, that all of the groundwater north of us is flowing through the sandstone and ends up coming out around our basement and in to the sump. during periods of heavy rain that could be quite a bit of water!

 

I know the pump(s) are working as I can see the water going out to the manhole and in to the RWH tank. so the only conclusion I can come to is that the pipe isn't wide enough to cope. although, it IS coping at the moment as the sump hasn't overflowed. but this whole thing is about mitigating the risk of the sump overflowing and so I'm leaning towards belt and braces and just putting the 50mm pipe in place and then forgetting about it (apart from yearly checks to make sure it's all working!). Also, if I do put the 3rd pump in connected to the 32mm pipe then I can do some magic where if the sump gets to the point of the high water alarm going off then I could automate supplying power to the 3rd 'summer' pump to aid in the removal of the water as I'd have a 50mm pipe AND a 32mm pipe which can only help.

[Thorfun]

thought I'd add the land drain and sump to the site layout drawing to show that we're collecting water from all around the basement and it all feeds to the sump

 

[saveasteading]

From my experience of pumps, the pipe at full flow with a strong pump is in danger of destroying the manhole it sits in...a powerful jet.

'at a fair whack' doesn't sound like manhole destroying force.

 

Also, I suggest wait and see....the groundwater may have been building up, and your pump may be reducing it to natural levels, and will then slow down.

 

Yes, you may be dewatering the whole area, which is another issue for another day perhaps.

[Pocster]

@Thorfun ; I can see now !

You are draining a big area 🙄

That can be a shit load of water on a rainy day ! . Pump away my friend . Belt ‘n’ braces all the way . I’m 4 pumps ( only 3 active at the moment ) and 2 sewer connections. You should certainly be doing no less .

[saveasteading]

OK. drawings very useful.

I should emphasise that I have not reviewed the previous 6 pages, so please excuse if this is already covered, and tell me.

 

You have a basement which should be watertight....a complex and precise construction. You don't then make a hole in the bottom of it to allow water into the house, then pump it out again.

The perimeter drainage needs to go away from the house. then there shouldn't be any need for sump or pump.

 

If the building has been designed for you then the designer should be resolving this....or the contractor.

 

[Thorfun]

3 minutes ago, saveasteading said:

OK. drawings very useful.

I should emphasise that I have not reviewed the previous 6 pages, so please excuse if this is already covered, and tell me.

 

You have a basement which should be watertight....a complex and precise construction. You don't then make a hole in the bottom of it to allow water into the house, then pump it out again.

The perimeter drainage needs to go away from the house. then there shouldn't be any need for sump or pump.

 

If the building has been designed for you then the designer should be resolving this....or the contractor.

 

the sump is external to the basement in a courtyard. the slope of the land is quite shallow and so the only way to remove the water from the land drain is via a pump as I'd probably have to go 500yds down the road to get to the level of the bottom of our basement!

[Thorfun]

so now I have @pocster's permission to carry on with the 50mm pipe solution 😉 anyone able to answer my questions regarding the step down from the basement to the courtyard ending up at 150mm? or minimum rebar cover for reinforced concrete if I need more than a 150mm step down?

 

I've answered the pipe question myself by finding this stuff https://www.sumpsandpumpsdirect.co.uk/acatalog/2-inch-Rigid-Pipe.html#SID=36 

[saveasteading]

11 minutes ago, Thorfun said:

to get to the level of the bottom of our basement!

Hence the house and courtyard should all be considered a basement....an inverse swimming pool.

Then there is no need for a pump of any sort.

 

This might be a fundamental design error, which would cost an awful lot to retrofix. So if  it is your own  work, sorry, and you cant be expected to know everything.. If by a professional then get them back.....or your insurers should be doing that for you.

 

[Thorfun]

Just now, saveasteading said:

Hence the house and courtyard should all be considered a basement....an inverse swimming pool.

Then there is no need for a pump of any sort.

 

This might be a fundamental design error, which would cost an awful lot to retrofix. So if  it is your own  work, sorry, and you cant be expected to know everything.. If by a professional then get them back.....or your insurers should be doing that for you.

 

well, the basement was designed by the structural engineer (from the architect's plans) and the drainage by the civil engineers but their drawings just say 'pump station by others'. there is no way to get the water from 3m down from ground level off the plot without a pump so I'm stuck with a pump solution and so will have to make it work.

[Thorfun]

34 minutes ago, Thorfun said:

so now I have @pocster's permission to carry on with the 50mm pipe solution 😉 anyone able to answer my questions regarding the step down from the basement to the courtyard ending up at 150mm? or minimum rebar cover for reinforced concrete if I need more than a 150mm step down?

 

I've answered the pipe question myself by finding this stuff https://www.sumpsandpumpsdirect.co.uk/acatalog/2-inch-Rigid-Pipe.html#SID=36 

so actually I can answer my own questions here. I've checked the architect's drawings and they state 150mm step down to the courtyard.

 

 

so I'm taking that as conforming to Building regs and so will crack on with laying a 50mm directly on the slab and then can lay the patio around it. I also need to fit a drainage channel/ACO to take patio surface water to the sump so should end up ok with levels etc.

[saveasteading]

1 hour ago, Thorfun said:

I'm stuck with a pump solution and so will have to make it work.

No. I don't see why you think you are responsible.  Or maybe I do.

 

The Architect has chosen to build a basement, extending outdoors. It should be completely waterproof from below and the sides..

Presumably (please!) the walls and foundation are designed to keep water out, as a basement with completely integrated waterproof structure (like a swimming pool o reservoir, but inside out.

Then the SE has made it work structurally.

 

Then someone has decided to dewater the flooded tank using a pump, of another's choosing.  I dont think so..Perhaps the reality is that  they didn't think it through and thought that the pump  is needed to dewater the patio, not the whole site.

And didn't think of the water getting in through the patio doors.

 

Back to basics.: this should not need a big pump, which by default is dewatering the entire area, except to take out direct rainwater landing in the patio. 

This could have been achieved if the sump was also sealed below*, and only the water from rain landing in the patio area.

 

If I was a cynical person, I'd be thinking that the architect has told you it is your problem, not their responsibility.

Hence you are going along with it, spending more and perhaps not resolving the fundamental design error.

 

I won't nag any more, as perhaps there are other reasons we don't know about. You seem determined not to trouble your designers, and to take all the cost and disturbance yourself.

And perhaps have an unsellable house.

This can be sorted by someone else if you want.

 

To me the design is wrong, it is the architect's responsibility and they should sort it.

I would write to them, and also the SE if they were engaged by you rather the Architect.

AND I would ask my insurer (and /or mortgager)  to look into it as a claim....They have the resources and clout to get this sorted at someone else's expense.

 

btw I showed your sketch to my wife, an accountant. She said immediately that the design was wrong and the designer should resolve.

 

 

The easy solution may be this * .Break out sump, and rebuild with integrated waterproof barrier beneath, fully linked to the house tanking.

divert the land drains away from the patio....whoever's idea was that?

[Thorfun]

3 hours ago, saveasteading said:

No. I don't see why you think you are responsible.  Or maybe I do.

 

The Architect has chosen to build a basement, extending outdoors. It should be completely waterproof from below and the sides..

Presumably (please!) the walls and foundation are designed to keep water out, as a basement with completely integrated waterproof structure (like a swimming pool o reservoir, but inside out.

Then the SE has made it work structurally.

 

Then someone has decided to dewater the flooded tank using a pump, of another's choosing.  I dont think so..Perhaps the reality is that  they didn't think it through and thought that the pump  is needed to dewater the patio, not the whole site.

And didn't think of the water getting in through the patio doors.

 

Back to basics.: this should not need a big pump, which by default is dewatering the entire area, except to take out direct rainwater landing in the patio. 

This could have been achieved if the sump was also sealed below*, and only the water from rain landing in the patio area.

 

If I was a cynical person, I'd be thinking that the architect has told you it is your problem, not their responsibility.

Hence you are going along with it, spending more and perhaps not resolving the fundamental design error.

 

I won't nag any more, as perhaps there are other reasons we don't know about. You seem determined not to trouble your designers, and to take all the cost and disturbance yourself.

And perhaps have an unsellable house.

This can be sorted by someone else if you want.

 

To me the design is wrong, it is the architect's responsibility and they should sort it.

I would write to them, and also the SE if they were engaged by you rather the Architect.

AND I would ask my insurer (and /or mortgager)  to look into it as a claim....They have the resources and clout to get this sorted at someone else's expense.

 

btw I showed your sketch to my wife, an accountant. She said immediately that the design was wrong and the designer should resolve.

 

 

The easy solution may be this * .Break out sump, and rebuild with integrated waterproof barrier beneath, fully linked to the house tanking.

divert the land drains away from the patio....whoever's idea was that?

we chose to build a basement, the architect just drew it for us. the basement is completely waterproof (with 2 forms of waterproofing) and no water has ever got in through the walls. building regulations required a secondary exit from the basement for fire regulations and so we chose to make that a sliding door out to a courtyard to make use of the outdoor space. these are all our decisions. no one forced us to have a basement or a courtyard. the only thing we were forced to do is have an egress. so maybe I should blame building control?

 

I understand where you're coming from and I appreciate you're trying to find someone to blame for our flood but I am to blame. I only had a single pump with no backup or alarm. I didn't hire a professional to design and install a pump station to deal with the water.

 

Also, the water has to go somewhere. the bottom of the basement is approx. 3.5m below ground level. where do you suggest we re-route that water? we're not on a steep slope to allow it to come above ground and so the only option is to keep it around the basement. but that's a really bad idea surely due to hydrostatic pressure. so we need to get rid of the water around the basement. the only solution is to feed it in to a sump and pump it out. so it's designed correctly, I just didn't install it properly. if I'd paid for someone to design the pump station and we then had a flood I would most definitely be speaking to them and making a claim. but that's not what happened.

 

 

[Mr Punter]

Can't you have paving on adjustable pedestals and run the pipework under it?

[Thorfun]

1 hour ago, Mr Punter said:

Can't you have paving on adjustable pedestals and run the pipework under it?

I have thought about this as we have this same solution on our balcony but my concern is that the slab underneath is not level and so the water that goes through between the patio slabs will just pool under the patio. if I were to use pedestals then I'd need to get the slab to fall towards the sump first so that it and the patio all drain their surface water in to the slab. maybe there is a solution that I'm unaware of though!

[Mr Punter]

Your drawing showed it laid to falls towards the sump and a channel.  If it is just a flat (ish) slab you would need to build some falls towards the sump before you use the adjustable pedestals and slabs.

[Pocster]

1 hour ago, Thorfun said:

I have thought about this as we have this same solution on our balcony but my concern is that the slab underneath is not level and so the water that goes through between the patio slabs will just pool under the patio. if I were to use pedestals then I'd need to get the slab to fall towards the sump first so that it and the patio all drain their surface water in to the slab. maybe there is a solution that I'm unaware of though!

My slab out the rear does indeed has a fall and funnels water towards the pump. I do have then level pedestals ontop. It might be possible to put a concrete 'topper' with fall on your patio slab. Or ( depending on layout ) simply break a channel in it so water equally runs towards pump.

[Thorfun]

2 hours ago, Mr Punter said:

Your drawing showed it laid to falls towards the sump and a channel.  If it is just a flat (ish) slab you would need to build some falls towards the sump before you use the adjustable pedestals and slabs.

yeah. exactly. so if I have to do that I might as well just lay the patio of a standard sand/cement mix to fall correctly. then it's solid underneath the patio and no water should get through.

[Thorfun]

so, another thought on our pumps. I wonder if I swapped the pumps for a tube float type pump that starts sooner if the 32mm pipe will be enough?

 

the current pumps start at 305mm depth of water

 

 

but they do a version with a tube float that starts pumping at 170mm

 

 

so, that would mean that there's less chance of the pump being able to cope as it starts pumping sooner, right?

 

I'm still thinking of doing the 50mm pipework but I thought maybe for now if I got one of the tube float pumps and swapped out the first pump I have and then monitored it all it might be better.

[Pocster]

14 minutes ago, Thorfun said:

so, another thought on our pumps. I wonder if I swapped the pumps for a tube float type pump that starts sooner if the 32mm pipe will be enough?

 

the current pumps start at 305mm depth of water

 

 

but they do a version with a tube float that starts pumping at 170mm

 

 

so, that would mean that there's less chance of the pump being able to cope as it starts pumping sooner, right?

 

I'm still thinking of doing the 50mm pipework but I thought maybe for now if I got one of the tube float pumps and swapped out the first pump I have and then monitored it all it might be better.

Is a ‘ tube float ‘ the tube with basically a ping pong ball in it ? 
These I found stick !

 

Given your situation I would leave current pump as is . Add a new 50mm pipe ( for another pump ) break out that pump recess so it’s larger . You can then have 2 pumps work in parallel each with an outlet ( 32mm and 50mm ) . If in doubt double up .

[Pocster]

You know I’m going to say Zoellar again don’t you 😁

[Thorfun]

30 minutes ago, pocster said:

You know I’m going to say Zoellar again don’t you 😁

yep. I know, I know. 😂

[Nickfromwales]

1 hour ago, pocster said:

Is a ‘ tube float ‘ the tube with basically a ping pong ball in it ? 
These I found stick !

 

Given your situation I would leave current pump as is . Add a new 50mm pipe ( for another pump ) break out that pump recess so it’s larger . You can then have 2 pumps work in parallel each with an outlet ( 32mm and 50mm ) . If in doubt double up .

Can you get these which use a reed switch or mercury? Much more reliable.

[Pocster]

Just now, Nickfromwales said:

Can you get these which use a reed switch or mercury? Much more reliable.

You just get a zoellar !

[Nickfromwales]

Mercury;

 

https://www.switchelectronics.co.uk/35-mercury-tilt-switch-12-5a-240v-s1116?gclid=Cj0KCQiAnsqdBhCGARIsAAyjYjT9ezoKqt5bEMJbKFcBV5HaeLLDrNzWCMBpD7E8QKxJ41rKRPETkTwaAjYbEALw_wcB

 

 

Reed;

 

https://www.switchelectronics.co.uk/no-reed-switch-aluminium-body-spst-ctc012