Pumps to Tank

I have a rainwater system that has been a mixture of fun and stress. The fun comes from the fact that the system is up and running potable water for my house. The stress has come from the rainwater pipes to my tank. Below is my system highlights:

- 3,400 sqft of metal roof
- 3" PVC painted black up to my gutters
- 3" PVC then runs underground to my Rain Tank
- 30,000 gallon rain tank


So my tank is about 6' lower than my roof so I am gravity fed for the most part. My problem is that there is enough pressure build on the 3" pipes going from my gutters > underground > up into the top of my tank. I keep having to dig up my pipe to repair leaky couplings (They were all primed and glued). Are there any large intake pumps 3" or 4" people have used to help the water flow during a rain storm? Any other community insight would be great. Thanks!

If you used drain pipe instead of a schedule 40, this could be the problem.

Another issue could be settling.  If the tank was not full of water when the pipes were added, it could be settling as it is filling,  putting pressure on the joints as it bends.

In either case i would replace the joints(couplers) with something that can flex.  Like a rubber connector over the outside with a clamp on each pipe.

Do either of these seem applicable?

Check this out at Amazon.com
EVERCONNECT 4825 Flexible Pvc Coupling with Stainless Steel Clamps, 2 inch, Black https://www.amazon.com/dp/B00HZSGWLG/ref=cm_sw_r_other_apa_RXDFBbEKVPNMN

How leaky are the failures underground?  If your pipe connected to the bottom of the rain barrel, then a pipe leak would be catastrophic.  But it sounds like your pipe does a "U" and then pours into the top of the tank.  I'd almost want a slow leak so that the pipe could empty out to prevent freezing when I'm not expecting it.  Note the word "almost".  A small drain valve would be better...

I can't envision how the pipe is holding any pressure.  Its open on 2 ends. Just curious, where is the overflow? Is it the gutter entry? Is the tank vented to displace air or does it have to chug through entry pipe?

If it's 9' from the gutter (inlet of pipe) to the ground and 3' back up to the top of the distant tank, the water level in the "U" of the pipe in a perfect world is right at the top of the tank.  Assuming that tank is 6' high, that gives a modest amount of pressure from the standing water in the piping.

Some pressure yes, but nowhere near the pressure it's capable of holding if its sch40. That little amount is a non issue. I would rule it out as a potential cause.

More info is needed.

Mike Jay wrote:If it's 9' from the gutter (inlet of pipe) to the ground and 3' back up to the top of the distant tank, the water level in the "U" of the pipe in a perfect world is right at the top of the tank.  Assuming that tank is 6' high, that gives a modest amount of pressure from the standing water in the piping.

Yes, it is from the pressure of the 6' high U. Also, this is schedule 40 PVC in clay soil that likes to swell. It only leaks during a good rainfall when it is exposed to the full pressure on the pipe.

I assume this is pressure related for large schedule 40 pipe as my septic contractor doesn't seem to have the same issues with the same pipe in the same soil.

I was wanting to see if there are any applicable pumps that I can setup with a float switch so the couplings are exposed to less pressure. I've found sprinkler pumps with larger inlets but am interested to see if anyone has already worked this out.

Thank you all for your input thus far.

I guess I'm still confused.  How much is leaking out?  I'm imagining a slow leak...  So when it's raining and the U is really flowing it leaks 1% or less.  Or is it more than that and it's making a muddy mess?

Are you thinking of putting a pump at the downhill end of the U to pump water up into the tank?  My guess is that you could arrange for a large sprinkler pump to push that water up into the tank for you.  But plumbing it and getting it to come on and off on a float could be a challenge.

If I understand the situation, it seems like fixing the leak is the real solution, a pump would be an expensive band-aid.  

But I could be totally misunderstanding...

Reading between the lines, are you saying its not the pressure of the sitting water, but the pressure of the clay on the pipes? Clay is dry, it gets wet,  its expands and applies external pressure on the pipe? Pipe shifts, coupler loses its seal?

Mike Jay wrote:I guess I'm still confused.  How much is leaking out?  I'm imagining a slow leak...  So when it's raining and the "U" is really flowing it leaks 1% or less.  Or is it more than that and it's making a muddy mess?

Are you thinking of putting a pump at the downhill end of the "U" to pump water up into the tank?  My guess is that you could arrange for a large sprinkler pump to push that water up into the tank for you.  But plumbing it and getting it to come on and off on a float could be a challenge.

If I understand the situation, it seems like fixing the leak is the real solution, a pump would be an expensive band-aid.  

But I could be totally misunderstanding...

It tends to become a muddy mess during a heavy down pour and over the last year I have replaced 3 couplings which involved digging up 20' of pipe so I could pull the pipe up enough to replace the couplings. I wish I had custom ordered longer couplings online as the home depot couplings are just 2" on each side which isn't enough seal for the torque of a 20' piece of schedule 40 on each side slightly moving.

The leaks are not excessive but I have the pipe buried 18" underground so I would rather not create any erosion issues.

I found these leaks by plugging the intake in my pioneer tank and connecting a water hose to my flush drain. At this point I am looking at a pump to prevent/minimize any new coupling leaks.

I dont see any method that would not leave the "u" full of water cause at somepoint the pump will push air. Air wont push the water up the "u", it will fall back down.


It seems that pumping would require an inner flexible pipe inside your pipe. The pump could be above ground. Like water falls in a barrel, sump pump pumps that through the old pipe (via inner pipe) into the main tank.

Ok, so when you dig out a leak, how is the pipe/coupling actually leaking?  Is the coupling breaking?  Or is it that the glue joint between the coupling and pipe is letting water squeak out?

Sorry for the silly question, but are you using the correct primer and glue for the plastic?  There are a number of different pvc glues and primers depending on the exact type of piping.

If the glue and primer are done properly, I think the plastic should break before the glue fails.  

Sorry, I know you are interested in a pump but I'm still stuck on figuring out the root cause of the issue.

Wayne, I think the leaks are only happening under the full force of rainwater coursing through the system.  When it's not raining the U doesn't leak.  At least that's how I'm reading it.

Mike Jay wrote:Ok, so when you dig out a leak, how is the pipe/coupling actually leaking?  Is the coupling breaking?  Or is it that the glue joint between the coupling and pipe is letting water squeak out?

Sorry for the silly question, but are you using the correct primer and glue for the plastic?  There are a number of different pvc glues and primers depending on the exact type of piping.

If the glue and primer are done properly, I think the plastic should break before the glue fails.  

Sorry, I know you are interested in a pump but I'm still stuck on figuring out the root cause of the issue.

Wayne, I think the leaks are only happening under the full force of rainwater coursing through the system.  When it's not raining the "U" doesn't leak.  At least that's how I'm reading it.

Yes, it is a leak between the coupling (broken seal). I used Purple PVC primer and Heavy Duty PVC solvent. Honestly I think the seal issue happens during application from laying such large and heavy pipe. To the posters hung up on coupling issues: Have you laid 3" schedule 40? This pvc-run circles my house and flows downhill to my tank so there is over 300' of pipe.

I'm an electrical contractor and have laid my fair share of conduit. The difference here being primer and water pipe. I have also worked on quite a few projects lately for homeowners with their own large rainwater systems similar to mine. A handful of them have similar issues so I was more generally curious about alleviating pressure in the pipes and minimizing the amount of potential leaks under ground.

When you search about pumps for rainwater there is a wealth of information about outake but nothing about intake. Surely, someone has a cistern or tank that they pump their rainwater up in to a tank??

wayne fajkus wrote:I dont see any method that would not leave the "u" full of water cause at somepoint the pump will push air. Air wont push the water up the "u", it will fall back down.


It seems that pumping would require an inner flexible pipe inside your pipe. The pump could be above ground. Like water falls in a barrel, sump pump pumps that through the old pipe (via inner pipe) into the main tank.

This has been my concern and reason for reaching out. I do think I could find a way of having a float switch turn it off as long as the pump could handle a dry run at the end of every rain. Also, I'd need to match a pump with a typical GPM provided by my gutters.

A sump pump will handle the volume and has a float switch to prevent dry runs. The downside is it won't clear all the water from the sump tank barrel. That 1/2" of water left behind will algae up, breed mosquitos, collect ick. Next rain event will put all that in the cistern. You would still need to run a smaller flexible hose into old pipe. Once the tank is full, will water still flow out of the cistern and into the cavity between outer and inner pipe? You never answered if you had an overflow built in. Where does it go?

There are companies that can inner sleeve the existing pipe. Not sure how it works. I found it one time when doing an exhaustive search on an inground pool with collapsing pipes.i ended up digging it up instead. Never pursued it.

I understand your angst. When you start understanding the other problems your solution may create, i cant help but think to fix the problem, not work around the problem.  The rubber flex joint. Or when you do dig and repair dump sand in the hole instead of clay since it is stable. Either allow it to move without deteriorating the joint, or do something to prevent the movement.

Its easy for me to say that. I am here, you are there. Lol

wayne fajkus wrote:A sump pump will handle the volume and has a float switch to prevent dry runs. The downside is it won't clear all the water from the sump tank barrel. That 1/2" of water left behind will algae up, breed mosquitos, collect ick. Next rain event will put all that in the cistern. You would still need to run a smaller flexible hose into old pipe. Once the tank is full, will water still flow out of the cistern and into the cavity between outer and inner pipe? You never answered if you had an overflow built in. Where does it go?

There are companies that can inner sleeve the existing pipe. Not sure how it works. I found it one time when doing an exhaustive search on an inground pool with collapsing pipes.i ended up digging it up instead. Never pursued it.

I understand your angst. When you start understanding the other problems your solution may create, i cant help but think to fix the problem, not work around the problem.  The rubber flex joint. Or when you do dig and repair dump sand in the hole instead of clay since it is stable. Either allow it to move without deteriorating the joint, or do something to prevent the movement.

Its easy for me to say that. I am here, you are there. Lol

LOL, thanks for the input Wayne. Most of the pipe is backfilled with sandy loam. I actually don't have a tank barrel and instead opted for a 1" bleed line that i leave open unless we are getting multiple days of rain.

I might try to find a way of creating a vacuum in the pvc so i can suck more PVC solvent into the leaking coupling (i think there is one left).

I'd still be interested in a direct inline pump. It wouldn't need a built in float switch, I can wire this separate to start the motor and place the float switch in an attached piece of pipe.

A pump may have to be 2000 gph, or 60 gallon per minute to alleviate the pressure while raining heavily on 3400 sq feet.

I like the flex couplings. Expansion joints like electrical conduit are not an option, and so flexible couplings and sections of pipe are used to alleviate forces and allow a seal with change of shape and alignment.

Additionally, pipe should be laid paying attention to thermal settling before backfilling. Pipe should be allowed to come to ground temp before burial.

Anchors could be made of concrete or wood, like a cradle block to bolster joints at critical areas or a switch to another type of pipe could be made.

Hunteric Thomas wrote:
Yes, it is from the pressure of the 6' high U. Also, this is schedule 40 PVC in clay soil that likes to swell. It only leaks during a good rainfall when it is exposed to the full pressure on the pipe.

FWIW the diameter of the pipe makes no difference to the pressure, only the height.

The water pressure from 6' of height is about 2.5 psi, 3" Schedule 40 is rated for 158 psi operating pressure.  A zip lock bag can withstand 2.5 psi.
Water pressure is not what is causing your leaks.

If it's leaking, either the joints weren't glued right, or as the others have suggested something is shifting and breaking the pipes

I am a bit lost as to how you know the underground pipes are leaking, just be observing without digging, can you explain.
Maybe it only starts leaking when you dig it out and shift stuff around.

It sounds like you installed this yourself and now you are still having trouble after months of trying to solve it.
I would be okay with bringing in some professional plumber and machinery to quickly solve the problem.

Why did you use a wet system vs a dry system? I didn't even think about the different type of systems