New Tub Drains Slowly

Newbie question, probably: I recently took out my old fiberglass shower unit and replaced it with a tub. Problem is, the tub has never drained very quickly - about a gallon a minute, by my rough calculations.
Here's what I have tried so far:
- disassembled the P-trap and drained the tub directly into a bucket, through its drain/stopper/overflow assembly only. No problem, very fast.
- examined the P-trap for blockages. None.
- snaked the drain pipe leading away from the P-trap. No blockages.
- snaked the vent pipe on the roof. No blockages.

The only change I made to the old drain setup was to replace the old trap with a new one. OK, there's a possibility that the slope is slightly different. It's hard to measure how far it drops in the three feet of drain pipe that I can see, it's probably somewhere between 1/2 and 1 inch max.

Any ideas on what else I can try? Any ideas?

Snaked the drain how? Why do you say "no blockage" when the drain rate of only 1 gal/min
is prima facie evidence of substantial blockage or other irregularity in the drain. Since it originally
drained a shower, the drain should be 2 inches. Is it? What material? How old?

The drain pipe is 1 1/2" black ABS. House is about 25 years old.

When I say that I snaked it, I mean that I was able to get a standard hardware-store snake - the coiled spring type - into it for about 3 ft without feeling any obstruction, at which point it hits a right-angle turn. Imperfect, I know. But if you truly feel that the drainage rate is can only be explained by a blockage (i.e. not a slope problem, not a venting problem) then I can take more radical steps to gain even more access - probably all the way to the standpipe. Is there anything else I should check before tearing into it that way? What if I shoved a garden hose into the pipe and put some pressure into it?

Most household snakes are between 15-25 feet long. Here in Vancouver there must be a clean out every 25' to insure that a line can be cleaned easily. If you are hitting a "Right Angle" at three feet that might be the blockage. Sometimes the snakes get caught on a poorly glued fitting. There is a lock nut on your snake (lock the nut) and try backing it in and out a little as you turn. This will build up a little tension in the snake and often it will jump over a lip.

You should be able to bury that snake 25' with little to no effort.

If not get a bigger snake and start below the tub if you need to.

I piped my tub with a nice 2" P-Trap and it drains faster than any tub I've seen to date. A slow draining tub is risky - one day the tub might be left on and it will overflow at the rates you mentioned.

Good luck. Keep trying the snake.

JW

As long as there is some slope, that would not cause slow drainage, although over time it leads to clogs. Lack of vent also does not cause slow drainage. The most common problem in tubs is hair right in the drain flange area, and in the trip lever plunger, it you have that type of stopper

quote;; . Here in Vancouver there must be a clean out every 25' to insure that a line can be cleaned easily

Your plumbers must not be able to afford good equipment, because in the U.S.A. it is every 75' and most plumbers have snakes at least that long. Stopping the snake because it reached a corner, is NOT snaking it properly.

Your plumbers must not be able to afford good equipment, because in the U.S.A. it is every 75' and most plumbers have snakes at least that long. Stopping the snake because it reached a corner, is NOT snaking it properly.

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We just prefer to work smarter! LOL What plumber wouldn't want more clean outs? The more the merrier!

Around here they frown on hard 90° elbows especially on the same plane. If we have to use 90° elbows, they prefer we roll them and combine them with a 45.