Here's a head-scratcher for you all. My bathtub and shower flow is very low but the sink next to it is 4x higher. The pipes that feed the sink continue to feed the tub. I've ran a bunch of flow tests for data. Both bathtub & sink have separate hot/cold handles.

1 Gallon Fill Time
Bathtub/Shower Hot Only: 1 minute 8 seconds
Bathtub/Shower Cold Only: 1 minute 8 seconds
Bathtub/Shower Both: 1 minute 8 seconds
Sink Hot Only: 25 seconds
Sink Cold Only: 22 seconds
Sink Both: 15 seconds

So, to me, this says that my pipe restriction is between the bathtub valves and spigot, especially because turning both hot & cold on the tub doesn't affect flow rate at all. Here's a picture of the piping for the 2 valves into the spigot.



Is it possible the brass valve stem/cross is the problem to all this restricted flow? Is that an easy part to simply replace? Ignore the duct tape; previous owners put it there because plaster was loosening. It is not part of the plumbing. Also ignore the copper cross pipe - it's bracing, not plumbing. It's a 1928 house.

Certainly seems to me, based on the data, that the restriction has to be right at the cross, where hot & cold mix. Otherwise, I'd see higher flows with both hot & cold on. It can't be in the spigot, because if so I'd see higher flows with the shower head vs. bathtub spigot. What are your thoughts?

 

I assume you have a three handle faucet in the tub. Have you tried removing the tub valve stem? I have seen debris get caught and restrict the flow. With the center diverter stem removed you could try opening the hot and cold sides to see if you get good flow into the diverter. If you get a strong stream of water then next I'd try removing the shower head and if you have the shower stopper on the tub spout I'd check it for a restriction.

 

It's a two-handle faucet. The bathtub spigot has the diverter on it to use the shower. I tested these flows with the tub spigot removed. Tub spigot is also new, just FYI.

Could there be debris caught right in the cross of the Two-Handle Tub Valve Body? Would you clean it from the bathtub side or replace it? Or, could brass restrict flow over the years compared to the copper pipe? I find it odd that turning on both hot & cold has no effect on either shower or bathtub flow.

 

Any other thoughts on this? Are there any tools/snakes I could consider using to run up the bathtub spigot into the brass valve yoke/body to dislodge anything that may be stuck in it?

 

I would next suspect the galvanized steel water lines. They often corrode shut hurting water flow and volume.

 

Could the brass valve stems/rough ins also corrode shut? I would normally suspect the galvanized lines, but I doubt their impact since turning on hot & cold together has no impact on water flow. Also because those pipes also feed the sink which has much higher flows.

Seems like the restriction is after hot & cold mix, but the only culprit then is the brass valve housing. I am perplexed.

 

The galvanized lines would be my first thought, but I see some logic in your tests too. And I sort of doubt that the manifold itself is the problem, but can envision the O rings, grommets, or whatever you have on the back end of the stems being swollen, deteriorated, etc. Sometimes a bugger, but usually not that bad of a job to get the stems out, and your local hardware will most likely have replacements on the shelf. A big box may have them too, but I have usually found a better selection at a real hardware store.

 

I guess the next step would be to turn the water off and remove the valve stems and have a look inside. If you don't see anything amiss I would be back to considering the steel pipes. It looks like at least the part visible in the picture is not feeding the sink so the problem could be in that section.

If you do have to test just ahead of your shower valve you could turn off the water and cut one line. Hose clamp a section of tubing/hose over the pipe and have someone turn the water on for a brief test. Then you could repair with a sweat on coupling or a Shark/Gator Bite fitting.

 

That's a great idea. If flows just ahead of the valve are still good, the problem has to be the valves.

 

Bumping thread as I've been thinking about this. Curious as to opinions here. As my 1st post stated, flows out of the bathtub spigot are the same whether I open hot/cold/both valves. So even if my valves were restricting flows, or the supply pipe was restricting flows, opening both should still see an increase, right? Two smaller, restricted flows combined together in the brass manifold should still be larger than hot or cold alone. That's what confuses me and keeps pointing me back to the manifold.

Would a brass manifold ever restrict like galvanized pipes?

The vertical shower line out of the manifold is galvanized - would internal rusting or mineral coating ever flake off and fall down (over decades) to block the manifold's center cross?

I was going to replace the valves first, but if I have to replace the brass manifold later, then the new valves would be a waste. Now I think I'll try Dane's advice and test water flow just before the manifold. If it's still good then the issue has to be the manifold. Right?

 

Galvanized and steel pipes are a problem eventually. If you've got the wall opened up I would replace them (with PEX) even if it's not the source of your flow problem. Replacing them now could solve the flow problem and prevent problems in the future.

As far as stuff from the vertical shower pipe falling down into the valve body... anything is possible. If it were happening I'd expect to see rust and other material getting clogged in the screen or aerator for the shower head.

 

Luckily for me, the brass valve body and supply pipes are accessible behind an access panel, so I don't have to open up the wall to run this test or replace the valve body (if needed). I agree if I had to open walls I'd just repipe everything and be done with it. Trying to avoid that for now, as I'd probably hire that out and replace the drain line at the same time, turning it into a pricey project.

 

That looks like a copper adapter soldered into the vertical in the cross. It looks like an excessive amount of solder to me. I’m wondering if whenever that plumbing was installed someone got some big gobs of solder down in that lower elbow which goes to the tub spout – which thus causes flow restriction right at the elbow.

But I can’t see the pic real well and might be out in left field (agaiiiin!!LOL)

(and I guess we would be talking about real gobs - LOL)

 

Yeah, that what it is. A copper female threaded adapter for the galvanized pipe running up to the shower head. It's soldered to the brass vertical. Well, regardless, I can run that flow test easily enough and if flows are good just before the brass valve body, I'll just replace the whole thing including valve stems and call it good.