Sealing pipes entering septic tank, proving difficult!

sas

Quick background first.

I chose to build a passive house using an insulated foundation system.
This means that all my soil pipes etc. leave the house through the floor.
This ultimately means that the pipes are much lower than standard 2 - 3 ft before they make their way to the septic tank.

The setup is that waste is gravity fed from the house to a septic tank. Planning was granted a long time ago so yes it's an actual septic tank.

The effluent leaves the tank again by gravity and feeds into a holding tank.
This tank contains a pump with a float switch.
When the float hits a certain level the pump kicks in and drives the effluent up to the percolation box.

I discovered over the last week that due to springs etc. caused by the weather etc. that both tank (holding and septic) are leaking ground water where the soil pipe enters the tanks. This has resulted in the pump running frequently and saturating the percolation area. We came within a couple of showers of backed up toilets!

So I got the track machine back on site to dig and we exposed the pipes. We also had a pump keeping the water level down so that we could attempt a reseal.

The photo below sums it up.



You can see the pipe linking the holding tank and septic tank fully submerged. I will say that at the time of this photo I was very pleased. Neither tank was leaking any water so I'd successfully sealed both. I used one of those new snag list emliminating sealants which allegedly even seal under water.



This evening I am deeply frustrated to see that after back filling the joints have failed again. The backfilling must have moved the pipe and broken the seal. They are much better than the were a week ago but I want them fully sealed.

Can anyone advise as to how this is normally done. I appreciate that my circumstances are not typical.
My current next move is to empty the tanks entirely and attempt to seal the tanks from inside i.e. no more digging and hence eliminate the risk of breaking the new seal.

Note: there is no option to draw the area around the tank to somewhere else. Due to all the above,we're simply too low in the ground and have no where to drain it to without using a pump.

All thoughts hugely appreciated or recommendations (by PM) on anyone that resolves such issues.

rayjdav

Sas,
You sure that this is your problem? The tanks are sound, moreover, the connections of the PCC risers?
I assume you have the internals of the tank outlet (T's) constructed properly.. If so, given the nature of the pre cast tank, outlet heights and the fit around the 4" pipe should be VERY tight, therefore very little "spill", if any. Even expa-foam would suffice to seal pipes.

From the pic there appears to be no protection to the outlet pipe to sump. Granular fill to side/top of this before backfill would help.

Very hard to tell without actual visual inspection. Best thing to do is get someone on site who knows (AT/Eng) what they are talking about otherwise you will just be digging it out time again.

bbam

I'd be thinking of a bitumen sealant as it will adhere well and maintain a good degree of flexibility. We've used it to seal slurry tanks and never had any bother since.

As for the high water table round the tanks I think I'd be digging down well and backfilling with clean stone to soak away as much water as possible. The idea of a sump with solar pump comes to mind to keep it down but I've no idea as to how good these pumps are.

Since the water table in your site seems so high you might want to rethink the size of the percolation area. With a high water table percolation is badly affected. I've had this in the past and during extended wet weather it may just back up anyway, maybe now you have the digger in look at extending it.

sas

rayjdav wrote: »

Sas,
You sure that this is your problem? The tanks are sound, moreover, the connections of the PCC risers?

The supervising Engineer was on site on friday morning and suggested sealing around the pipes with a sealant such as the one I used.

Water ingress around the pipe is definitely the problem. The holding tank has a pump which empties it. When it's empty the water could be seen streaming over\around the pipe entering it. It's very obvious.

The risers are above the water level on site so it's not that on this occasion. I've pretty much stood looking into the tanks for 2 days. The surface of the water in them can be seen being disturbed etc. so it's obvious where the water is coming from. We also lowered the level in the 2nd chamber of the septic tank below the outlet pipe in order to allow us to see if water was streaming in there too and it was.

rayjdav wrote: »

I assume you have the internals of the tank outlet (T's) constructed properly.. If so, given the nature of the pre cast tank, outlet heights and the fit around the 4" pipe should be VERY tight, therefore very little "spill", if any. Even expa-foam would suffice to seal pipes.

The tank was installed following the details of the supplier. The fit around the pipes isn't very tight. I was there when it was put it. It took some effort to get the pipe in but it was far from perfect in my opinion.

I wasn't aware that expanding foam is water proof. With respect, is this a proven solution or theory? I'm dubious of the many miraculous uses of expanding foam.

rayjdav wrote: »

From the pic there appears to be no protection to the outlet pipe to sump. Granular fill to side/top of this before backfill would help.

Very hard to tell without actual visual inspection. Best thing to do is get someone on site who knows (AT/Eng) what they are talking about otherwise you will just be digging it out time again.

Then entire tank including pipes was backfilled with clean 20mm chip. This is part of the problem. It's allowing the spring to bubble up too easily. The hole behind the tank in that pic is 3 foot deep. It fills from empty in about 4 hours. We emptied the water again before backfilling.

Eng. was on site as you recommended.

In the pic, we had dug the hole, emptied it and then I applied the sealant. It was left over night. The pic is from the next morning i.e. I believe this to be as bad as the water level will get.

When we installed the tank we were down about 9 ft with no sign of ground water. This may be a temporary condition given how bad the weather has been. It will also be an ongoing problem too though if the weather is a factor.

My main concern is the percolation area being overwhelmed i.e. ground water gets into holding tank, pump drives it into percolation area. This is what happened over the last 2 weeks on a couple of occasions. I'm going to try and determine this morning how long it takes for the tank to fill and pump to kick in.

My secondard concern is the electricity usage of pump kicking in alot more often than planned. I haven't looked at the specs for the pump though so can't determine the cost on that yet.

Thank you for your suggestions.

SAS

sas

bbam wrote: »

I'd be thinking of a bitumen sealant as it will adhere well and maintain a good degree of flexibility. We've used it to seal slurry tanks and never had any bother since.
.

Will look into this.

bbam wrote: »

As for the high water table round the tanks I think I'd be digging down well and backfilling with clean stone to soak away as much water as possible. The idea of a sump with solar pump comes to mind to keep it down but I've no idea as to how good these pumps are.

The entire tank was back filled with stone. The stone allowed the water to enter easily. When we started digging were were around 4 foot from the edge of the tank and down 4 - 5 ft . No water at all. Then we broke through to the stone around the tank and it flowed through. We could see a couple of springs rising as we dug. Solar pump would be an interesting idea but may not be much use i.e. in wettest conditions we also get little sun.

bbam wrote: »

Since the water table in your site seems so high you might want to rethink the size of the percolation area. With a high water table percolation is badly affected. I've had this in the past and during extended wet weather it may just back up anyway, maybe now you have the digger in look at extending it

Percolation area is already substantial. I didn't scrimp here. It was built to the letter of the law. I stood over them as it was done with regs in hand. The base of the stone in the percolation trenches is about level with the water level in the pic. So unless there's upward soakage, that may not be the biggest contributor to this.

Thanks,

SAS

Fries-With-That

sas wrote: »

Quick background first.








This evening I am deeply frustrated to see that after back filling the joints have failed again. The backfilling must have moved the pipe and broken the seal. They are much better than the were a week ago but I want them fully sealed.

If it was me, and I'm not an expert in this area, I would backfill (gravel and rock) the area between the two tanks with the pipe removed to about 1 foot below the level of the pipe inlets.

I would then construct a sealed shuttering box on top of this about 1 foot square so that the pipe will run through the box and connect both tanks.

Use a good quality sealing product to seal the box at its joints and either end.

Use a good quality sealing product to seal the pipes into both tanks (make sure the tank inlets are dry).

Once the sealant has had the correct amount of time to dry I'd either back fill the shuttering box with concrete or use a fine sand that you could remove if the sealant fails at a future date.

My logic on the concrete is the water won't seep into the openings around the tanks even if the sealant fails.

Best of luck with the problem.

steifanc

sas wrote: »

Quick background first.

I chose to build a passive house using an insulated foundation system.
This means that all my soil pipes etc. leave the house through the floor.
This ultimately means that the pipes are much lower than standard 2 - 3 ft before they make their way to the septic tank.

The setup is that waste is gravity fed from the house to a septic tank. Planning was granted a long time ago so yes it's an actual septic tank.

The effluent leaves the tank again by gravity and feeds into a holding tank.
This tank contains a pump with a float switch.
When the float hits a certain level the pump kicks in and drives the effluent up to the percolation box.

I discovered over the last week that due to springs etc. caused by the weather etc. that both tank (holding and septic) are leaking ground water where the soil pipe enters the tanks. This has resulted in the pump running frequently and saturating the percolation area. We came within a couple of showers of backed up toilets!

So I got the track machine back on site to dig and we exposed the pipes. We also had a pump keeping the water level down so that we could attempt a reseal.

The photo below sums it up.



You can see the pipe linking the holding tank and septic tank fully submerged. I will say that at the time of this photo I was very pleased. Neither tank was leaking any water so I'd successfully sealed both. I used one of those new snag list emliminating sealants which allegedly even seal under water.



This evening I am deeply frustrated to see that after back filling the joints have failed again. The backfilling must have moved the pipe and broken the seal. They are much better than the were a week ago but I want them fully sealed.

Can anyone advise as to how this is normally done. I appreciate that my circumstances are not typical.
My current next move is to empty the tanks entirely and attempt to seal the tanks from inside i.e. no more digging and hence eliminate the risk of breaking the new seal.

Note: there is no option to draw the area around the tank to somewhere else. Due to all the above,we're simply too low in the ground and have no where to drain it to without using a pump.

All thoughts hugely appreciated or recommendations (by PM) on anyone that resolves such issues.

I had the same problem , what we did was dug a big soak pit deside the tank filled it with large rubble broken blocks ect and took a pipe from the pit all the way to the land drainage ditch . No problem since . Note the hole was larger and deeper then the tank

sas

Fries-With-That wrote: »

If it was me, and I'm not an expert in this area, I would backfill (gravel and rock) the area between the two tanks with the pipe removed to about 1 foot below the level of the pipe inlets.

I would then construct a sealed shuttering box on top of this about 1 foot square so that the pipe will run through the box and connect both tanks.

Use a good quality sealing product to seal the box at its joints and either end.

Use a good quality sealing product to seal the pipes into both tanks (make sure the tank inlets are dry).

Once the sealant has had the correct amount of time to dry I'd either back fill the shuttering box with concrete or use a fine sand that you could remove if the sealant fails at a future date.

My logic on the concrete is the water won't seep into the openings around the tanks even if the sealant fails.

Best of luck with the problem.

Thanks, I'd been considering something along this line. Basically shuttering a 'u' shaped concrete section joining the 2 tanks with the pipe floating in that. Basically with stone\sand. Concrete is too permanent for me.

sas

steifanc wrote: »

I had the same problem , what we did was dug a big soak pit deside the tank filled it with large rubble broken blocks ect and took a pipe from the pit all the way to the land drainage ditch . No problem since . Note the hole was larger and deeper then the tank

The problem for me is that the area is prone to springs so I could simply dig and uncover another one which would fill the soak pit rendering it useless.

We're simply too low in the ground. If we were at the typical height for a septic tank this issue simply wouldn't be occurring. I need to accept the water and try and keep it out of the system I reckon.

The amount of water getting in now may not be terribly significant. It's certainly alot less than a week ago.

I'm going to monitor the percolation area and sump tank on an on going basis.
If I need to take further action I'll consider options then.

rayjdav

steifanc wrote: »

I had the same problem , what we did was dug a big soak pit deside the tank filled it with large rubble broken blocks ect and took a pipe from the pit all the way to the land drainage ditch . No problem since . Note the hole was larger and deeper then the tank

Hope I misread that.
You dug a soakpit for effluent runoff and then drained it to a ditch?:eek:
Jebus. Who gave you that bright idea
If I took you up wrong, apologies in advance but if not, christ......

muffler

I came across a similar situation a few years ago where the treatment unit was basically put into a "hole" on the site. It was located in the only part of the site where the surrounding ground was falling towards the tank on all sides thus ensuring that there was a continuous flow of surface water running into the tank.

The pump was basically running 24/7 and while there was an option to dig around the tank and back fill with stone and pipe this to a lower part of the site where there was an open drain the ground levels were going to remain the same.

As the unit was placed about 5 metres from where it was supposed to go and as there was a good decent fall from the house we got the suppliers/installers back again and got them to remove the inlet pipe, lift the tank out of the ground completely, fill the hole with 1 metre deep of stone and then blinding and place the tank back on top of this.

Effectively the tank was raised by a metre which left the float above the highest level of surrounding water but the site levels allowed for this and that may not be applicable in the current situation.

sas

muffler wrote: »

I came across a similar situation a few years ago where the treatment unit was basically put into a "hole" on the site. It was located in the only part of the site where the surrounding ground was falling towards the tank on all sides thus ensuring that there was a continuous flow of surface water running into the tank.

The pump was basically running 24/7 and while there was an option to dig around the tank and back fill with stone and pipe this to a lower part of the site where there was an open drain the ground levels were going to remain the same.

As the unit was placed about 5 metres from where it was supposed to go and as there was a good decent fall from the house we got the suppliers/installers back again and got them to remove the inlet pipe, lift the tank out of the ground completely, fill the hole with 1 metre deep of stone and then blinding and place the tank back on top of this.

Effectively the tank was raised by a metre which left the float above the highest level of surrounding water but the site levels allowed for this and that may not be applicable in the current situation.

Unfortunately the tank is already as high as possible while maintaining the recommended falls from the house. Even if we went for planning again there isn't anywhere else on the site that the tank could be placed while meeting the regs re distances from drains, boundaries, the house itself.

The issue is that the pipes leave the house about 800mm below finished floor level of the house due to the insulated raft.

Having discussed this with the engineer this morning, we're confident that sealing the tank in position is the only way to go. The how is up for debate. He's recommending bitumen or preferably concrete. My concern with concrete is that if that fails, there's no going back.

sydthebeat

just had a quick look at the percolation test results for that site....

T = 10

and the test was done in april !

:D:D:D:D

sas

sydthebeat wrote: »

just had a quick look at the percolation test results for that site....

T = 10

and the test was done in april !

:D:D:D:D

I've no idea what this means. Site was bought with OPP so I don't know if any shenanigans were involved because I didn't do the test.

PaleRider

Is there any possibility of draining the water away from around the septic tank. Can you post more photos of site. What size is the site. Is the site flat? Can you post site layout drawing - section drawing.

It may be that the T-Values are correct for percolation area - If this area is not giving trouble?
It could be that in digging the hole for the tank you disturbed a confining layer of clay over a aquifer? However there can be any number of reasons why something doesn't work. Can i get a look at the site assessment?

sas

PaleRider wrote: »

Is there any possibility of draining the water away from around the septic tank. Can you post more photos of site. What size is the site. Is the site flat? Can you post site layout drawing - section drawing.
?

We checked the levels on site using a laser level and unfortunately the level of the water in the pic equal with or slightly below the lowest drain available to us. There is no option to gravity feed away the water to an existing drain\soak pit.

I could post a photo of the site but I'm not sure what it is I should show in them. The site is relatively level. It does slope up hill from the road but we are talking a climb of 0.6 - 1m max over 70 metres i.e nothing significant.

I don't have a section drawing.

PaleRider wrote: »

It may be that the T-Values are correct for percolation area - If this area is not giving trouble?

I don't know yet if the percolation area is giving trouble. While the sump tank was taking on ground water it was overwhelming the percolation area. Until this has had a few weeks to recover I can't comment.

PaleRider wrote: »

It could be that in digging the hole for the tank you disturbed a confining layer of clay over a aquifer? However there can be any number of reasons why something doesn't work. Can i get a look at the site assessment?

If aquifer means "spring" then this is pretty much what happened I believe. We dug to about 10 ft for the tank and did see some evidence of a spring at the very base. We back filled around both tanks with 20mm chip which is likely allowing the water up.

If we could be sure of not hitting a spring we could simply dig a large soak pit nearby and pipe the top of the water away until it's at a level that is not interfering with the pipes. There are no guarantees though so adding further expense for no guarantee of success is not attractive.

OPP was granted about 6 years ago (not to me) so I'm not sure there was a site assessment. I'm not even sure what a site assessment is or what it would look like. I'll take a look through what documentation I do have.

EDIT: I checked on line and there is nothing bit a prelinary site layout plan and percolation results in terms of site documentation on the OPP application.

Thanks

SAS

PaleRider

Sorry I meant to replay sooner. Let me know if things get better or worse. Flat sites leave less options. At the moment I can't add anything to this problem.

sas

PaleRider wrote: »

Sorry I meant to replay sooner. Let me know if things get better or worse. Flat sites leave less options. At the moment I can't add anything to this problem.

Hi,

Things had improved alot up to last night.

The percolation pipes were pretty much dry and the leaks into the tanks had reduced to a very small thin film of liquid running down the wall of the tanks. I suspect this was due to the water level having reduced over the last few days.

When I got up this morning and saw big puddles all over the bag "garden", I will admit to being concerned.

I will take a look at things when I get home this evening and see if the rain last night has made things worse.

Thanks,

SAS

stock>

Try this product..............

Sika®-2 Water Plug
Leak stopping for high waterpressure Sika 2 is a ready to use rapid setting leak stopping liquid which is mixed with ordinary portland cement to produce a paste for rapid leak sealing against high water pressure infiltration.

Close Details
Use
To seal against high water pressure infiltrations in concrete, rock or masonry
Allows Sika 1 renders, gunite or shotcrete to be applied on structures exposed to running surface water
Characteristics and Advantages
Does not require diluting
Rapid setting time
Just add ordinary portland cement
Well proven
Does not contain chlorides

http://irl.sika.com/en/solutions_products/02/02a009/02a009sa03/02a009sa03100/02a009sa03101.html

This stuff is available from a good builders providers..

Stock

esox28

http://ie.wavin.com/master/master.jsp?FOLDER%3C%3Efolder_id=2534374305439306&PRODUCT%3C%3Eprd_id=845524442247619&middleTemplateName=oc_middle_product_detail_I

sas maybe have a look at this..

what you will need to do is disconnect the connector pipe between tanks and inlarge the hole in the tank to recieve the rubber sealer only using a core drill make sure the hole is perfectly round, then reconnect the pipe using a repair collor in the middle of pipe to make life easy to join the tank connectors

sas

esox28 wrote: »

http://ie.wavin.com/master/master.jsp?FOLDER%3C%3Efolder_id=2534374305439306&PRODUCT%3C%3Eprd_id=845524442247619&middleTemplateName=oc_middle_product_detail_I

sas maybe have a look at this..

what you will need to do is disconnect the connector pipe between tanks and inlarge the hole in the tank to recieve the rubber sealer only using a core drill make sure the hole is perfectly round, then reconnect the pipe using a repair collor in the middle of pipe to make life easy to join the tank connectors

Very promising. Looks alot more along the lines of what I'd need.

rayjdav

esox28 wrote: »

http://ie.wavin.com/master/master.jsp?FOLDER%3C%3Efolder_id=2534374305439306&PRODUCT%3C%3Eprd_id=845524442247619&middleTemplateName=oc_middle_product_detail_I

sas maybe have a look at this..

what you will need to do is disconnect the connector pipe between tanks and inlarge the hole in the tank to recieve the rubber sealer only using a core drill make sure the hole is perfectly round, then reconnect the pipe using a repair collor in the middle of pipe to make life easy to join the tank connectors

Sas,
Be very careful if you do this as it is a pre-cast unit and any further fail, the manufacturer will run a mile, and rightly so.
These tanks are supplied to take standard dimensioned pipes (110mm), giving tight fit. Would be next impossible with core bit to enlarge hole a couple of mm as bit's are supplied as standard too.
I would, if had to use a sealing product, go with @stock> suggestions first.

sas

An update:

The leaks into the tanks have stopped for now. I'm assuming the water level has dropped below the level which resulted in issues.

However, my percolation pipes were entirely full last night so I'm once again heading home with spade in hand. This time I'm not blaming water from the sump tank due to ground water. The pipes filled entirely in 24 hours. The percolation area pipes have capacity to store over 500 litres of water. Difficult to accept that a house with no one home during the generated that much water.

My theorys are as follows:

(a) Holes in percolation pipes are too small and in frequent. I followed the drilling pattern to the letter of the regs which I gather isn't "standard practise", that being the process of hacking gashes in the pipes with a con saw. This isn't based on anything other than big holes means quicker water release.

(b) The percolation trenches are flooding due to ground water. This could be a disaster as it could mean a raised percolation bed and money I don't really have. Engineer is already talking about this. I'd prefer to determine where the water is coming from first!

(c) The digger man did something in my absence which I naively didn't question at the time. The rain water from the garage (large roof) is being diverted into a trench that runs perpendicular to the percolation trenches i.e it's about 8 foot from the end of the trenches. However this was backfilled with stone and the vent pipe from the percolation trench passes through this on its journey to the surface. There may well be a direct connection (through the chippings) between the rain water trench and the percolation area. This would explain alot. I talked to the digger man on it this morning and he believes I may be correct as regards the setup. The rain water pipe is also likely above the height of the percolation trench.

First job this evening is to dig down the side of one of the trenchs about half way along and see if the chippings are holding water. If they are then that likely rules out (a) above.

I'm also going to pipe the rain water away from here and towards the road which should have been done in the first place.

The battle continues...

DM_7

Maybe try waterstop. You can read about it on the bostik website.

it fills gaps of up to 10 mill. Its a polymer based product that can be used on wet surfaces. It is flexible, strong and fastdrying.

Comes in a big tub, small tin or tube depending on how much needed. I used it to seal a riser last year and it did a great job.

EDIT: sorry I posted the above before reading about new problem! Good luck with it. I had to put in a raised bed last year (thats where the riser issue came from) hopefully your problem just stems from the amount of ground water that got pumped in this last week or so and is only a temporary issue.

sas

sas wrote: »

(a) Holes in percolation pipes are too small and in frequent. I followed the drilling pattern to the letter of the regs which I gather isn't "standard practise", that being the process of hacking gashes in the pipes with a con saw. This isn't based on anything other than big holes means quicker water release.

My investigation efforts have me satisfied that this is not the case.

sas wrote: »

(b) The percolation trenches are flooding due to ground water. This could be a disaster as it could mean a raised percolation bed and money I don't really have. Engineer is already talking about this. I'd prefer to determine where the water is coming from first!

Jury is out on this one. I managed to drain the percolation area to the depth of the bottom of the highest point of the pipes i.e. level with the bottom of the pipes in the percolation box.

I kept house and garage away from this for a few days. There was a slight increase in water level on tuesday night after 2 days of rain.
On tuesday night I reenabled the pump from the sump tank and although the pipes are half full in the percolation box, this is holding after 2 days.

sas wrote: »

(c) The digger man did something in my absence which I naively didn't question at the time. The rain water from the garage (large roof) is being diverted into a trench that runs perpendicular to the percolation trenches i.e it's about 8 foot from the end of the trenches. However this was backfilled with stone and the vent pipe from the percolation trench passes through this on its journey to the surface. There may well be a direct connection (through the chippings) between the rain water trench and the percolation area. This would explain alot. I talked to the digger man on it this morning and he believes I may be correct as regards the setup. The rain water pipe is also likely above the height of the percolation trench.

I've temporarily solved this. Permanent solution to follow.

It may the case that the percolation area was saturated by rainwater from the garage getting to it and hence we need to nurse it back to health.
Naturally this is what I'm hoping for. I've made my peace with the idea that I'll likely be looking into the percolation box every 1 - 2 days for the next few years.

steifanc

rayjdav wrote: »

steifanc wrote: »

I had the same problem , what we did was dug a big soak pit deside the tank filled it with large rubble broken blocks ect and took a pipe from the pit all the way to the land drainage ditch . No problem since . Note the hole was larger and deeper then the tank

Hope I misread that.
You dug a soakpit for effluent runoff and then drained it to a ditch?:eek:
Jebus. Who gave you that bright idea
If I took you up wrong, apologies in advance but if not, christ......

Yep you read it wrong , the soak pit is to take the surface water away and stop it filling my tank , my tank is quite low too , the effluent is pumped to a percolating 60m away from the tank and 180m2