sump pump plumbing

[mound]

Looking for some insights into how my sump pump discharge is plumbed.

The line extends up from the pump, but then splits off as in the attached pic.  One line discharges outside the house, I believe it's the line with the valve inline with it. I've only ever seen water "trickling" out of the outside of the house when the pump is running, certainly not even close to a full pressure discharge.  The other line, I'm assuming, is going out to the storm drain though I can't trace it as the basement is finished.  I see no indication that it's hooked back into the sanitary sewer line. 

Discharging into the storm drain is acceptable according to town code (I've been told) but I'm confused then about why it splits off also to the exterior, why there is a valve inline with that split, and why despite the valve being all the way closed, some water still exits the house into the yard..  Is this some sort of fail-safe in case the storm drains are full?  if so, is that valve supposed to be manually opened in the event the storm drains are full or is the trickling water despite it being closed, correct? Or are my assumptions completely wrong?

In 15yrs I've never had water in the basement but the pump itself is now failing, so faced with replacing it I'm trying to figure out why it is as it is.

thanks for any insights!

[WoodTinker]

Looking for some insights into how my sump pump discharge is plumbed.

The line extends up from the pump, but then splits off as in the attached pic.  One line discharges outside the house, I believe it's the line with the valve inline with it. I've only ever seen water "trickling" out of the outside of the house when the pump is running, certainly not even close to a full pressure discharge.  The other line, I'm assuming, is going out to the storm drain though I can't trace it as the basement is finished.  I see no indication that it's hooked back into the sanitary sewer line. 

Discharging into the storm drain is acceptable according to town code (I've been told) but I'm confused then about why it splits off also to the exterior, why there is a valve inline with that split, and why despite the valve being all the way closed, some water still exits the house into the yard..  Is this some sort of fail-safe in case the storm drains are full?  if so, is that valve supposed to be manually opened in the event the storm drains are full or is the trickling water despite it being closed, correct? Or are my assumptions completely wrong?

In 15yrs I've never had water in the basement but the pump itself is now failing, so faced with replacing it I'm trying to figure out why it is as it is.

thanks for any insights!

Fill the sump with some colored dye and turn on the pump and see where the colored water comes out.

[Robert Adams]

Maybe it's just in case the storm sewer backs up. Or maybe the PO put a hose on the fitting outside the house and would use that water to say water the yard away from the house. 
 
       If that pipe exits right outside the house don't leave that valve open. You want that water away form the house.

[mound]

Maybe it's just in case the storm sewer backs up. Or maybe the PO put a hose on the fitting outside the house and would use that water to say water the yard away from the house. 
 
       If that pipe exits right outside the house don't leave that valve open. You want that water away form the house.

Odd thing is though with the valve completely closed, water still comes out.. not fast, not a lot, but it comes out.. maybe the valve itself is bad..

[Robert Adams]

Odd thing is though with the valve completely closed, water still comes out.. not fast, not a lot, but it comes out.. maybe the valve itself is bad..

              Looks like a gate valve and I bet it was a used valve when installed. That valve is expensive new and the local BORGs don't carry much in the way of valves over 1". So probably not closing all the way but most of those can be taken apart and cleaned and rebuilt.

[Ridgeway]

Maybe it's just in case the storm sewer backs up. Or maybe the PO put a hose on the fitting outside the house and would use that water to say water the yard away from the house. 
 
       If that pipe exits right outside the house don't leave that valve open. You want that water away form the house.

Bingo.

We have that issue here.

We can have flood situations where the sump pump is on and the storm sewer is backing up.  In that case you need the excess water to go somewhere, preferably outside the house.

[Stwood_]

Yes. Faucet washers can be bought for those.
I just put one in a outside spigot, saving myself 20 bucks over a new spigot.

[TDKPE]

Since the valve branches off lower than the main discharge, I'd have to agree with RA that the valve is not closing all the way and some small amount is bypassing.  There's a bit of gravity head, plus pump head, pushing against that valve.  I'd just drain that line down to the pump and pop the valve off the body.  Prolly just some crud on the gate.  It's not like it has to hold back significant pressure, as it was designed to do, so just a bit of cleaning and maybe lubing should get it to close fully (or close enough).

But do use two wrenches on it if you open it.  That plastic won't hold much without breaking.