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