Low tub spout GPM from Moen 2510

[Zopkios]

I’ve installed a Moen T2252EP and 2510 PosiTemp pressure balancing shower valve. Because I wasn’t happy with the shower flow rate, I removed the flow restrictor in the shower head.
So that’s fine now. But I am not pleased with flow rate for the tub. The tub spout is free and clear of any flow restrictor. There are no restrictive fittings between the tub spout and valve.
I disassembled all the supply lines to the 2510, checking in particular the one leading to the tub spout.
But I found no blockages anywhere.

I even removed the cartridge and separated tested the hot and cold flow. Although I didn’t measure the GPM when doing this, the water easily reached the other end of the tub, a very strong flow.
I don’t have low water pressure in the house. Water flow through the laundry tub faucet is very good as you would expect, there being no — flow restrictors.
The shower flow rate is good since I removed the flow restrictor.
Shut-off valves to the 2510 are lever type ball joint and are fully open.

I checked to see if I had the cold and hot reversed but they're correct.

I removed the chrome tub spout to be sure it wasn’t hampering the flow — no difference.
There isn’t an excess of elbows, just the ones shown in the photos.

Below the floor, the supply lines are each less than 10 feet from the main lines running through the basement. Both are 1/2 inch copper but the cold comes from a 3/4 inch copper line.
I measured the GPM — it is 3.5.

The PSI is 80.

So according to Moen, the GPM at that PSI should be at least 6.3 GPM.

Moen sent me a replacement 1222B cartridge — no difference.

I even removed the same cartridge from the shower downstairs and tried it — no difference.

With the shower downstairs, I tried it with the other cartridges and it works properly, same as the original one it it.

So what could be wrong — why am I getting just 3.5 GPM out of the tub spout?

 

[hj]

Did you remove the white plastic "stabilizers" from the Sharkbite fittings? They are just for plastic pipes.

 

[Sponsor]

 

[Zopkios]

Did you remove the white plastic "stabilizers" from the Sharkbite fittings? They are just for plastic pipes.

Interestingly, I did make that mistake but have since removed them from all the fittings shown in the photos. However, there may still be some in the fittings below the floor. I will check that out and remove any I find. But truth be told, I would be surprised if that were the problem. That's because of the strong flow in both lines I observe when I remove the cartridge.

 

[Zopkios]

Interestingly, I did make that mistake but have since removed them from all the fittings shown in the photos. However, there may still be some in the fittings below the floor. I will check that out and remove any I find. But truth be told, I would be surprised if that were the problem. That's because of the strong flow in both lines I observe when I remove the cartridge.

Since replying, I went downstairs and was about to proceed checking out the fittings. And I will still do that, if necessary. But I got to thinking that since Moen allows the use of PEX, not just copper, those plastics would be there for PEX. That being so, do you still believe it would be the source of the problem?

 

[Terry]

Just to be sure, when the Moen rotates to on, it's cold at first and then rotates over to the hot water side.

Is the valve body upside down? It's marked which side is up.

 

[Zopkios]

Just to be sure, when the Moen rotates to on, it's cold at first and then rotates over to the hot water side.

Is the valve body upside down? It's marked which side is up.

That's how it's working for me, starts off cold and gets hotter as you turn it. No, it isn't upside down, reads "HC".

 

[Jadnashua]

The shower outlet usually has a smaller opening...it usually is the upper outlet.

The openings in the cartridge are smaller than the supply pipes, so there is some restriction in it versus just a straight pipe. Just to verify...the pipe from the valve to the tub spout is copper?

Are there any threaded fittings? Did you use tape on them? If you're not careful, you can get some tape over the pipe opening, potentially decreasing flow.

 

[Zopkios]

Yes, I have the shower connected to the top hub. No tape on the CU to male thread adaptors connected to the 2510. I used pipe thread compound. 1/2 inch copper pipe used throughout. Flow from the shower head is more than adequate, maybe even too much after I removed the flow restrictor.

 

[Zopkios]

Yes, I have the shower connected to the top hub. No tape on the CU to male thread adaptors connected to the 2510. I used pipe thread compound. 1/2 inch copper pipe used throughout. Flow from the shower head is more than adequate, maybe even too much after I removed the flow restrictor.

I am thinking of trying yet another replacement cartridge, not a Moen but one by Plumbshop. I wouldn't normally go with a non-Moen replacement part. But Home Depot in the two nearest towns does not stock the Moen 1222B. Besides, compared to the $20 one by Plumbshop, the Moen costs about $50. It is worth taking a $20 gamble to see if it solves the problem. Besides, if I am careful opening the packaging, I can re-package and return if it makes no difference. If it does solve the problem, then I'll contact Moen for a genuine part replacement. Still, I must say that I would be surprised if it works, given that 3 Moen cartridges have already been tried. Nothing to lose but my sanity!

 

[Jadnashua]

The symptoms you have seem to match what someone else already said...some debris in the supply lines that moves, giving you an initial high flow, then the restriction as that debris butts up against something, slowing the flow. IF that's the case, no cartridge is likely to solve your problem.

Does that Moen design have a separate balancing spool valve? IF so, that may be the issue. Some designs have that internal to the cartridge, some use a separate one.

 

[Zopkios]

No balancing spool valve on the 2510. You are right about an obstruction of some kind being the problem. It is likely plastic sleeves which may still be in the Shark-bites. At the time, I did not realize they were to be removed if not using PEX. But apart from those restricting flow, there may well be an obstruction of some kind. Given what I've already established, you are also right about the problem having nothing to do with the cartridge. So I've changed my mind about trying the Plumbshop one. I will disassemble the supply lines below the floor today and see what's what. And report what I found!

 

[Zopkios]

No balancing spool valve on the 2510. You are right about an obstruction of some kind being the problem. It is likely plastic sleeves which may still be in the Shark-bites. At the time, I did not realize they were to be removed if not using PEX. But apart from those restricting flow, there may well be an obstruction of some kind. Given what I've already established, you are also right about the problem having nothing to do with the cartridge. So I've changed my mind about trying the Plumbshop one. I will disassemble the supply lines below the floor today and see what's what. And report what I found!

No balancing spool valve on the 2510. You are right about an obstruction of some kind being the problem. It is likely plastic sleeves which may still be in the Shark-bites. At the time, I did not realize they were to be removed if not using PEX. But apart from those restricting flow, there may well be an obstruction of some kind. Given what I've already established, you are also right about the problem having nothing to do with the cartridge. So I've changed my mind about trying the Plumbshop one. I will disassemble the supply lines below the floor today and see what's what. And report what I found!

Another failure! Just finished disassembling the supply lines underneath the bathroom floor. Found 4 Shark-Bite sleeves, removed them and put everything back together. Now I can say that the supply lines from the 2510 valve to the main lines are "sleeve-free". Also removed the copper pipe from the 2510 to the tub spout. Checked for any obstruction, there is none. While the tub spout line was removed, I pushed a coat hanger wire up into the 2510 to see if there was an obstruction. Result ended up being inconclusive. That's because it of course is at the bottom so no visual. I would have expected the wire to have gone up farther and felt more of an open space. I am at a big disadvantage because I don't remember what is inside that exit hub on the 2510. Home Depot does not stock the 2510. Neither do other places around here. Otherwise, I would go there and see. It looks right now that the only remaining possibility is the 2510 itself. That's where an obstruction has to be. Before I go to all the work of removing it, can anyone tell me how I might verify that the tub exit on the 2510 is clear of an obstruction?

 

[Zopkios]

The symptoms you have seem to match what someone else already said...some debris in the supply lines that moves, giving you an initial high flow, then the restriction as that debris butts up against something, slowing the flow. IF that's the case, no cartridge is likely to solve your problem.

Does that Moen design have a separate balancing spool valve? IF so, that may be the issue. Some designs have that internal to the cartridge, some use a separate one.

There is no "initial high flow" -- it's a constant 3.5 GPM. BTW, I've seen a suggestion elsewhere to connect the bottom port to the shower and the top port to the tub spout. In the present situation I have going on, it does seem that there is a greater GPM coming out of the shower but I haven't actually measured it as I did with the tub spout. Even if that would work, giving me a much greater GPM at the tub spout, why would it be necessary to do that? It would be what I call a "hollow victory".

 

[Jadnashua]

People have found small bits of plastic, a small stone, etc., in their pipes that produce the sort of problem you are experiencing. Things work okay until they are forced against an elbow or other area they can't move beyond while blocking some of the flow. It could also be a blob of solder or something else. Some valves have filter screens on their inlets...if yours does, they could be partially clogged.

FWIW, while the stiffening inserts in Sharkbites (any fitting used with pex will have a similar device) generally aren't that great of an obstruction. The Bernoulli principle applies to a short length obstruction...the fluid speeds up through the obstruction then slows back down again afterwards, resulting in only a very minor overall flow hit. Of course, the more of those you have, those small increments do add up. The flow tables give you an idea of the dynamic pressure and volume available as you add those up.

 

[Zopkios]

Well, I certainly cannot rule out that possibility of a small piece of plastic, stone, etc. farther down in one of the supply lines and thank you for alerting me to that possibility. But since my last post, I've taken everything above the floor apart and removed the 2510. No obstructions whatsoever. When I reinstalled the 2510, I definitely have the it facing up as it was before as per the "up" on the 2510. Now that I've been made aware of the possibility of a small obstruction, I will check the remaining 5 feet or so on each line. Both go straight into the main lines. So if there were a small stone that was causing the problem, there was a far greater chance finding it in what I disassembled both today and yesterday. Still, I will check. This is one of those kind of problems which a person can "live with" since the shower is unaffected and all which is wrong is that the tub takes twice as long to fill. So it is just an annoyance and not much more.

 

[Jadnashua]

If there are any shutoffs along the water path, ensure that they are all fully opened. Well, sometimes, it works better if you open fully, then turn back a smidgen...otherwise, on some designs, they can tend to seize up. It's often best to be able to turn it both ways a little when you need to access it to free it up rather than having it fully at one end of its travel. All you need is a few degrees, and that does not apply to 1/4-turn, ball valves.

 

[Zopkios]

Good thing to check, for sure. But in my case, there are none other than a ball type on the cold water supply which enters the water heater. It's turning out to be a mystery and a half as to why the low GPM from the tub spout yet a more than adequate GPM from the shower head. Wondering now if, yesterday when I disassembled everything to the 2510, I should have put the top down. But even if doing that increased the GPM at the tub spout, why would it have been necessary? Moen marks it "top" for a reason.

 

[Zopkios]

Since my last post, I altered the supply lines so as to eliminate elbows and offsets which aren't necessary. And relocated the shutoffs from behind the tub/shower to the lines below the tub -- see attached photos. In doing so, I flushed both supply lines in the basement just to be sure there wasn't a stone or other obstacle which was restricting flow. No difference, another failure. This is turning out to be "one for the books". I've done everything as suggested by Moen and people in here. Totally baffled! BTW, I even tried capping off the shower at the head. No difference.