Septic tank connection to drainpipe

[bcarwell]

I have a small (500 gal) septic tank servicing a little guest room and am adding a graywater perforated drainpipe/field horizontally off the tank. On the side of the tank is a cylindrical cowling or flange (collar ?) that protrudes out from the side of the tank wall maybe 3 inches. It is obviously intended to receive the drain pipe. If you feel inside the cowling on the outer wall of the tank with your finger there is a circular groove about 4 inches in diameter that appears to be a knock out for insertion of a standard 4 inch drainpipe into the cowling and hence the tank.

The problem is the cowling i.d. is about 4 1/2 or 5 inches in diameter such that when I insert the 4 inch drain pipe in it there is a spacing or annulus of maybe 1/2 inch or so between the outer surface of the drainpipe and the inner surface of the cowling.

The question is: what is the standard way to connect the drainpipe to this cowling (which by the way is not threaded). Is there a standard reducer fitting which press fits OUTSIDE and AROUND the cowling and reduces down to a 4 inch cowling that the drainpipe can slide into tightly ? Or do you fill the space/annulus between the cowling and the inserted drain pipe with some sort of silicon caulk or foam or grout that adheres to PVC ?

The kind folks at Lowes are clueless and obviously not plumbers though they work in the plumbing department.

Thanks for any help.


Bob

 

[tommu56]

Some time there is a rubber donuts that you fold up in hole and grease up the pipe and slide it in similar to this in page 41 of the catalog gasket for hub fittings.

http://www.tylerpipe.com/documents/catalog2008web.pdf

What make is the tank maybe the mfg has info on it.

The norwesco ones I use have outlet and inllet mounted in them and you just glue in the pipe they fit 4' sdr34 and schedule 80.

They also have a gasket but I've never used them.

http://www.norwesco.com/PDF/WWMGASKETKIT61765.pdf

tom

 

[radioman]

Is the septic tank concrete and old ? some tanks use the oakum rope as gaskets to seal the pipe. Its about 1/4 to 1/2 inch thick rope. Oakum is basically tarred fiber rope. Nowadays the oakum are not tarred but still readily available for those odd/old unique jobs.

 

[Topstrap]

Most of the tanks I have installed usually have a rubber insert cast into the tank that you can knockout and has different size scored lines for 3" or 4"SD or 4"sch 40 pipe to give it a good seal. Some you just knocked the thin concrete casting out and slid the pipe in and either tarred, concreted or used an expanding foam to seal it. On the ends you have to be careful when you slide the pipe in that you don't get too close to the baffle but on the sides you should be OK. I'm guessing you mean that inlet is near the inlet end of the tank and side inlets usually don't have a baffle straight in front of it but to the side.

Not sure what you have on the side of that tank unless it does take a seal like someone else mentioned. As long as it goes in and you can get a good seal around it all inlets are usually higher than what the outlet will be so it shouldn't have a chance of leaking unless something causes the effluent to back up in the tank.

Topstrap

 

[bcarwell]

Thanks to all for the quick and helpful replies.

The tank is plastic, polypropylene I'm guessing, maybe 7 years old. Can't tell what brand since its buried. Didn't want to waste effort digging up the input side since I was only looking for the outlet port to attach the drainfield pipe to it. But it appears that the outlet port I found is on the side and the input is on the front.

It looks like one of the gaskets above should do the trick crammed into the outlet collar and then sliding the 4" pipe in it (e.g. the gaskets or donuts appear to be thick enough to serve the same function as a foam or the tarred rope you all mentioned in filling the gap between the collar i.d. and the drainpipe o.d.

Topstrap, the only scoring I found was inside the collar on the wall of the tank and it is one 4" circle obviously intended as the drainpipe knockout. But as I noted the i.d. of the collar is more like 5 inches leaving about a 1/2 inch gap between the inside surface of the collar and the outside surface of the drainpipe. Once I knock out the knockout I'll feel inside to make sure I don't shove the pipe in too far contacting any baffle.

So... looks like I'll hunt for a gasket and failing that will fill the annulus with a sealing foam. I might be able to find some sort of reducer I can install and glue around the outside of the collar that will receive the drainpipe that I can glue to the receiver but so far I haven't found one of the right dimensions.

Thanks again.

Bob

 

[JB4310]

Thanks to all for the quick and helpful replies.

The tank is plastic, polypropylene I'm guessing, maybe 7 years old. Can't tell what brand since its buried. Didn't want to waste effort digging up the input side since I was only looking for the outlet port to attach the drainfield pipe to it. But it appears that the outlet port I found is on the side and the input is on the front.

It looks like one of the gaskets above should do the trick crammed into the outlet collar and then sliding the 4" pipe in it (e.g. the gaskets or donuts appear to be thick enough to serve the same function as a foam or the tarred rope you all mentioned in filling the gap between the collar i.d. and the drainpipe o.d.

Topstrap, the only scoring I found was inside the collar on the wall of the tank and it is one 4" circle obviously intended as the drainpipe knockout. But as I noted the i.d. of the collar is more like 5 inches leaving about a 1/2 inch gap between the inside surface of the collar and the outside surface of the drainpipe. Once I knock out the knockout I'll feel inside to make sure I don't shove the pipe in too far contacting any baffle.

So... looks like I'll hunt for a gasket and failing that will fill the annulus with a sealing foam. I might be able to find some sort of reducer I can install and glue around the outside of the collar that will receive the drainpipe that I can glue to the receiver but so far I haven't found one of the right dimensions.

Thanks again.

Bob

How about a Fernco type coupling, that would give you a good connection. They make every size imaginable, depending on the outside of that collar, maybe a 5x4.

Fernco Couplings, Flexible Couplings, Flexible Pipe Connectors, Fernco Fitting, Shielded Couplings, Fernco Donut, Pro-Flex Coupling, Large Diameter Couplings, Sewer, Drain, Waste, Plumbing Flexible Couplings, Plumbing Pipe Leak Repair | Fernco

Fernco Flexible Coupling, fernco, fernco coupling, fernco couplings, fernco fittings, Sewer Flexible Coupling, Plumbing Flexible Coupling, Drain Flexible Coupling, Waste Pipe Flexible Coupling | Fernco

A 4" schd 40 coupling might slip into that bell end pretty snugly, then you would adapt down to your pipe.

But doesn't your system have a leech field already?
Also what type pipe are you referring to by "drain pipe"? I don't think corrugated slotted ADS would be good, you'd need the pipe with the ~1/2" holes layed along the bottom.

JB.

 

[Topstrap]

I just got back in and had measured a 4" sch 40 coupler today and it's exactly 5" on the outside. It should fit perfectly for you inside that coupler. I was looking for a Fernco rubber coupler also for claytile thinking it might be big enough also. I think I can picture what you have so you might have to put a short insert into your knockout then slide that 4" sch 40 connector onto that pipe and shove that whole thing into the larger plastic coupler you have? Prob more confusing that it really is but at least you have options now and a solution we think.

Good luck

Topstrap

 

[bcarwell]

Thanks again all. Looks like a coupler is the way to go and I'm sure I can find Fernco's. BTW in answer to the question I do <not> already have a leach field, and that is what this is all about- adding a 30 foot single "drainpipe" off the 500 gall. septic tank into a ditch with gravel and sand underneath for greywater. The little guest house gets such little use that the original owners apparently just intended to pump the septic tank occasionally and not bother with running a leach line off it. And what I refer to as the "drainpipe" is just three standard 10 foot sections of 4" pvc with the 1/2 inch holes.

Thanks again fellers ! Great help.

Bob

 

[Highbeam]

You want that connection to be sealed well because the septic tank outlet actually pulls effluent from the "clear zone" of the tank about 16" below the surface. Any leakage at the outlet will be skimming the top of the tank contents which is the scum. The scum is fats, oils, and grease that you don't want going out into your drainfield.

You would normally grout that connection or I've even used hydraulic cement on a tank that was in use. Lowes will sell the hydraulic cement by the bucket and it is amazing stuff.

 

[tommu56]

high beam is right!
In side tank there should be a tee with a short length of pipe (12") looking down and second in the top of the looking up and side to the out pipe

The hard scumb line should stay in the middle of the tee between the two pipe ends.

The effeluent should be mostly clear coming in the bottom of the pipe up to the side outlet and down to the drain field.

here is a link as to what it should look like.

http://www.inspectapedia.com/septbook.htm

tom

 

[JB4310]

Yup as the two previous posters stated you need some kind of a baffle to prevent the floating crap (when can you ever use that word as the literal definition ) from skimming off the top and fouling up your leaching system in short order.

Still find it hard to believe someone would go through the trouble of installing a septic tank with no leach field. What did they do have a flush counter, so they would know when it was full?

JB.

 

[Highbeam]

We get lots of folks putting in "holding tanks" for site that aren't good for septic or if it is just a temporary deal. It turns out that a septic tank is very cheap to buy and have set. Down around 70 cents per gallon vs. most tanks at over 1$ per gallon. They're good tanks but not usually put in without a drainfield because the local health departments don't consider it a permanent solution to have to pump out the holding tank occasionally.

If it was me, I would have an overflow to show me when it was too full but also would check it often through one of the smaller baffle access lids. Nothing is worse than sewage backing up.

 

[MarkV]

Every place is different so this may not apply. In my area 1000 gals of tank and 150' of field is minimum. Doesn't matter if you are talking never used, barn bath or full time small house. Could be a big issue if it were disclosed, as required in a future sale.

MarkV

 

[bcarwell]

Thanks again ! Tommu56 and Highbeam: what is the purpose of the upper part of the T going up ? Why isn't it just an elbow joint facing down ? Seems the scum layer could rise up above upper part of the T and run into the T and out into the leach field. I'll feel for the T when I knock out the punch out on the side of the tank as I'm wondering if even my little cheapo 500 gallon septic tank would have such a T or would they expect you to add it if you are adding an output/leach field line. And I'll have to try that "hydraulic cement". Never heard of it before ! BTW a semi plumber type guy at Lowes said to seal with that expanding foam stuff and said that's what they use. Is he right or is grout the preferred sealant ?

 

[Western]

One thing I wish we had added to ours was a junction box or manifold (not sure of the proper term) Basically an access point between the leach field and last tank.

Someday I may have to add a floating foam or crystal root killer and that would eliminate going through 2 tanks.

 

[JB4310]

Thanks again ! Tommu56 and Highbeam: what is the purpose of the upper part of the T going up ? Why isn't it just an elbow joint facing down ? Seems the scum layer could rise up above upper part of the T and run into the T and out into the leach field. I'll feel for the T when I knock out the punch out on the side of the tank as I'm wondering if even my little cheapo 500 gallon septic tank would have such a T or would they expect you to add it if you are adding an output/leach field line. And I'll have to try that "hydraulic cement". Never heard of it before ! BTW a semi plumber type guy at Lowes said to seal with that expanding foam stuff and said that's what they use. Is he right or is grout the preferred sealant ?

Not to speak for them, but but the reason for the tee is, easier to inspect and clean if necessary, and possibly acts as a vent like in the house to prevent siphon, but not sure about that. The 90 would work but would not be easy to clean and inspect. The old tanks I've seen just had a steel plate across the opening acting as the baffle.

You could have a short riser on it to prevent any high floating stuff from going over the top, but the water level would stay at the height of the bottom of the pipe, which is about 6 inches from the top of the tee. Not sure but some may have a riser up to ground level, that would make for easy inspection.

So I take it you have not uncovered the top of the tank to look in there? As far as if there is a tee now in there, I am not familiar with modern septic systems, but would suspect that if knock out is not stubbed for pipe and is designed to slip pipe thru, that there may not be a tee in there. Though you did mention there is that collar or flange built in, so maybe there is something in there.

I personally would pump the level of the tank down before I knocked that plug out or stuck my hand in there for inspection, sounds like an episode of "Dirty Jobs"

JB.

 

[tommu56]

the top of te tee should have a 12" piece of pipe in it when some one flushes toilet you want to be able to see the effluent going up the lower leg of the tee and out the side by looking down the the upper section.

don't use foam for the seal use a sealer gasket or hydraulic cement.

as JB4310 pump tank down slide pipe in through knock out glue tee assembly on pull it back out some but so you can see down manhole and see the tee.

some times there is some sort of baffle is cast in side the tank to eliminate the tee thingy

tom

 

[Highbeam]

My tee doesn't have a stub running up. Just the top of the tee which is where I shove in the effluent filter. The scum level should never come up in the tank. The scum is only slightly less dense then water and will displace water to almost the level of the bottom of the outlet pipe. That outlet pipe should always remain either empty or flowing out at the exact same rate that it flows into the tank through the same size 4" pipe. So You should not expect the level of the tank contents to rise and fall at all in the tank meaning that you don't need a top riser.

Truth be told, I take good care of what goes into my tank and my scum layer has only ever been 1/4" thick and missing in places. Scum is fats, oils, and grease and you shouldn't be dumping that down the tank. It slowly will be digested as well so some input from people washing and dishwashing will make it to the tank only to be digested. In my case, the sludge from below accumulates fastest.

Oh yes, it needs to be a tee. The drainfield must remain aerobic to provide secondary treatment. It needs air moving through it and the drainfield will vent into the septic tank which vents out through the stack vent in your house. Do not use a 90.