Ok to change this sanitary tee to a long sweep combo?

[Dougster]

Three drains (kitchen, laundry and tub/shower) block in unison every couple of years and the clog has always been cleared at the downstream sanitary tee shown below.

It has been suggested I replace this abrupt fitting by a long sweep combo.

This seems to make sense because I can’t see any need to admit vent air upstream into the lateral drains at this location since all three upstream fixtures have their individual sanitary tees, vents and traps. I also thought san tees were only effective for short laterals or low volume waste flows.

I would appreciate comments explaining any reason not to go ahead with the change.

I’d also like to know why a sanitary tee might have been required at this location in the first place. E.g. was it a toss up between a sanitary tee and a combo in the original code and why?

BTW this is a 58 y.o. single story two bath California tract home with a basic cast iron / galvanized DWV. The building sewer out to the street may be clay or cast iron.

Thanks.

(The two views are at right angles to each other):

 

[Asktom]

I can't see where changing that fitting would help, except it would let you see how gunked up that horizontal run is. I am quite sure that is where the problem is.

 

[Sponsor]

 

[Reach4]

Is there a vent for the shower after the shower drain? If no, then you would not be OK to just get rid of the santee for a combo. Now as far as that pipe carrying water from three things to that santee, I don't know if that is allowed.

 

[Dougster]

ask tom :

• The horizontal lines will be replaced up to the combos below the upstream fixtures, at least.
• Whether to keep the sanitary tee style connection might still be an open question since in one instance after snaking the line at the kitchen, the clog was only cleared after snaking down from the lavatory (using a hand snake).

Reach4:

• Yes, the tub/shower has a vent (indeed all three upstream fixtures have their individual traps, sanitary tees, and vents).
• The capacity of that horizontal 2” pipe into that sanitary tee appears to be within spec since the maximum in the IRC is 6 DFU while in the UPC it’s 8, vs my 3 fixtures which total 6.

ALL:

• I just realized from the photos that the outlet of the sanitary tee appears to be a spigot connected directly to the hub of the combo underneath. So maybe the long sweeps available to the tract plumbers would not fit??
• Is there a style of long sweep combo fitting that would fit?

 

[Asktom]

There is no need to change the san tee. Your setup is normal and a bazillion of them are working across the nation.

 

[hj]

The T is NOT the problem.

 

[Dougster]

Ok, so there’s no point to replace that san tee with a long sweep combo.

I will still have a plumber replace the 2” galvanized lateral drain pipes which are all in the crawlspace. These service the KS, LT and tub / shower.

• Is the best plan to simply cut the GI pipes just after each of the three Wye clean outs and just before that san tee, and then swap in the new pipes using banded rubber couplings?
• Should the new pipes (and intermediate Wye and bend fittings) be ABS, PVC, or, do I stay with Galv & cast iron?

[The goal is to stay in the house for 20 more years "DWV-service-free" after which it will probably become a tear-down.]

Thanks. These photos start at the kitchen and progress down to the san tee:

FACING NORTHEAST

FACING NORTHWEST

FACING NORTHWEST

FACING SOUTH

FACING WEST

 

[Reach4]

the clog has always been cleared at the downstream sanitary tee shown below.

That seems to be very significant. If you are confident that is where the clogs have been, the change to a combo or wye+45 sure seems like a good idea. And maybe add a cleanout while you are making changes. I am not a plumber.

If the plug was at the san tee under discussion, running water in the kitchen would back up into the shower.

 

[Bluebinky]

That looks exactly like my Santa Clara house (other than a slightly different grouping of drains) just up the road from you. About once a year, we (and many of the neighbours) get the same clog like yours. The short-term fix takes about 10 minutes with a small consumer-grade snake. One neighbour claims he had the lateral drain properly "snaked out" (by a competent plumber, not some ***-drain-*** company) to remove the massive amounts of rust, and has been clog-free for about 6 years now.

 

[Cacher_Chick]

The iron/galvanized horizonal run is very likely full of scale from corrosion, which creates a restricted/slow drain, with the solids building up until the priblem becomes obvious. If the line were being rodded with a mechanical rodding machine and a properly sized head, most of the scale could be flushed out of the line and the drain would be likely to work fine for several years. Replacing the primary horizontal run with PVC will also be an effective way to get rid of the bulk of the problem. It would be quick and easy to cut out and replace just that and it might be fixed for a long time to come.

 

[Dougster]

If the plug was at the san tee under discussion, running water in the kitchen would back up into the shower

Backup into the tub/shower is exactly what happens. Last instance was April'14 and we were running either the laundry or the kitchen sink when the clog again attained critical mass. I agree that weekly use of the laundry probably helps flush the line and the san tee - thus extending the clog-free state -- up to a point.

The iron/galvanized horizonal run is very likely full of scale from corrosion, ...Replacing the primary horizontal run with PVC will also be an effective way to get rid of the bulk of the problem. It would be quick and easy to cut out and replace just that and it might be fixed for a long time to come.

A highly restricted lateral is certainly correct. The reason for my original post was to try to understand if it's practical and worthwhile to replace the san tee with a long sweep combo as a side job (the side jobs are the killers!).

That seems to be very significant. If you are confident that is where the clogs have been, the change to a combo or wye+45 sure seems like a good idea. And maybe add a cleanout while you are making changes. I am not a plumber.

I think the only way to do add a special cleanout for the san tee is via a wye cleanout in the upstream lateral. However that would be in the crawlspace whereas the existing kitchen sink cleanout is already accessible at the exterior wall.

Re. switching the san tee to a long sweep combo, I mentioned above there might be a clearance issue since the height of the incoming lateral is already established by the overall system design. It looks like the current san tee has a spigot outlet that plugs directly into the hub of the combo underneath and perhaps that's why they used it i.e. the inlet to the tract builder's san tee was at precisely the correct height to match the incoming lateral whereas a long sweep combo would be too high to line up. I didn't get any feedback on this sub-topic and am still curious what the forum thinks.

I am also still curious whether it's best to replace the lines with ABS, PVC or new galvanized. One problem with ABS is it's extra work to get straight ABS pipes. Many local remodels and rebuilds are happy with the new ABS vent pipes coming out the roofs all cockeyed like wilted flowers, which doesn't bode well for their laterals.

 

[Asktom]

The san tee is fine, don't worry about that. ABS is common in some areas, PVC in others. If you are going to use plastic fittings availability in your area is the issue, and it sounds like ABS is the deal where you are. If you just change straight lengths you could use either ABS or schedule 40 PVC pipe and the proper shielded couplings. ABS does expand (thus bend) more than PVC. As for the wilted flowers, if the pipe protrudes 6" above the flashing that is all you need - not much wilting can occur at that length.