Questions on replacing washer drain standpipe

[Noah Katz]

My girlfriend's parents got a new washing machine that apparently has a much higher discharge rate out of the drain hose than their decades-old previous machine, so the 1 1/2" standpipe (house is 65 yr old) can't handle the flow.

She got a quote for $1500 to replace the standpipe with a larger one, as well as the old water supply valves.

What I'm wondering is, won't it have to neck down to mate with what I presume is a reducing T in the sewer drain pipe?

I expect that would greatly limit the increase in flow rate.

I wouldn't think that $1500 would include digging underneath the house's slab foundation to replace the T; tis is a high labor rate area (San Francisco peninsula).

The only mitigating possibility that I can think of is that the pipe is bigger below the P-trap.

I'd appreciate some clarifying knowledge.

 

[breplum]

I actually did what you are describing: Put in a 2" p-trap in the wall without replacing the 1-1/2" pipe going past the room itself.
1. I replaced the trap on principle, not because of a back up.
2. It would have been impropper for galvanized steel 1-1/2" pipe to be used under a slab. It has never been legal...only cast iron...and cast iron would have been 2" when the slab was poured.
That is a high price (I say that as someone who charges ~$250/hr.) depending on what they are going to do. It should include opening up sheetrock. Always get a few small shop to quotes.

 

[Noah Katz]

> It would have been impropper for galvanized steel 1-1/2" pipe to be used under a slab.

This is what I was thinking is in there:



> I actually did what you are describing: Put in a 2" p-trap in the wall without replacing the 1-1/2" pipe going past the room itself.

My concern is still that the necking down at the top of the T will be too restrictive; when I was emptying the tub it took only several sec to fill a 3 gal bucket.

I calculate the volume of the pipe and trap above the T as 0.3 gal, so it will get filled very quickly.

But I'm just guessing.

Is solving the problem something I should expect to be guaranteed if we show him how fast the washer drains?

> That is a high price (I say that as someone who charges ~$250/hr.) depending on what they are going to do. It should include opening up sheetrock.

I hope it's too high.

I know the quote included opening the wall, but not if it included a complete patch job.

Thanks

 

[breplum]

I would have NEVER reduced the 2 x 2 x 1.5" tee on a paying customer's job, but I did it at my house and it has worked fine for years with modern Samsung washer

 

[Noah Katz]

> I would have NEVER reduced the 2 x 2 x 1.5" tee on a paying customer's job, but I did it at my house and it has worked fine for years with modern Samsung washer

Good to know, but I'm not at all confident that it will work out for us as well.

So this question remains:

> Is solving the problem something I should expect to be guaranteed if we show him how fast the washer drains?

 

[Geofd]

Most codes are changing from 1 1/2 piping to 2" piping right to the main, I just put a second laundry in my house and used 2" 1st because of code 2nd because for the cost of 11/2+2" pcv is not a deal breaker

 

[Pipe Dreams]

Most codes are changing from 1 1/2 piping to 2" piping right to the main, I just put a second laundry in my house and used 2" 1st because of code 2nd because for the cost of 11/2+2" pcv is not a deal breaker

it has been 3 inch for me for 15 years

 

[Pipe Dreams]

My girlfriend's parents got a new washing machine that apparently has a much higher discharge rate out of the drain hose than their decades-old previous machine, so the 1 1/2" standpipe (house is 65 yr old) can't handle the flow.

She got a quote for $1500 to replace the standpipe with a larger one, as well as the old water supply valves.

What I'm wondering is, won't it have to neck down to mate with what I presume is a reducing T in the sewer drain pipe?

I expect that would greatly limit the increase in flow rate.

I wouldn't think that $1500 would include digging underneath the house's slab foundation to replace the T; tis is a high labor rate area (San Francisco peninsula).

The only mitigating possibility that I can think of is that the pipe is bigger below the P-trap.

I'd appreciate some clarifying knowledge.

"Standpipe"

the vertical pipe after the trap...or the pipe that the washer drains into.

So it would seem like the quote would only be for replacing that. 1500 would be too low for concrete work.

Some picture would be good

 

[Noah Katz]

The fix was to reduce the discharge rate with a ball valve.



There are those who are probably thinking this is a bad idea because the pump motor might overheat.

It's counterintuitive but restricting the output of a centrifugal pump actually reduces the load because instead of having to accelerate new incoming water, the same water just goes around in circles inside the pump.

A common example is a shop vac which (also a centrifugal pump but with the fluid being a gas instead of a liquid) where if you block either the input or the output the motor speed increases because the load is decreasing.

 

[Geofd]

Have you checked with an appliance guy or the appliance brand you have the ball valve may void any warranty if there is one

 

[Noah Katz]

I thought about that but dismissed it as improbable.

Meaning that it would specifically mention anything like that, not that they wouldn't deny coverage if they knew about it, but one hose clamp and it's gone.