What water supply flow rates should I maintain for my home

[Rossn]

I am looking into filtration options for my home, and one consideration is whole house carbon filtration.

The products have advertised flow rates that would limit the overall flow rate to the home. I do have a 1" city supply leading to the mechanical room.

My home is 4.5 baths, where 1 bath is dedicated to a single-bedroom rental unit, which would have it's own kitchen area and laundry (so, 2 kitchens (only one dishwasher), 2 laundries in the home). Master bath has two shower heads. There are only three of us in the rest of the home, though we do sometimes have guests. All this means regularly 4 people in the home + intermittent guests.

What flow rate should I be sure to maintain through any filtration?

My typical pressure is 60-65 psi, and I assume any whole house filter would have some pressure drop across it.

 

[Terry]

I have some information on this link.

https://terrylove.com/watersize.htm
Four bathrooms, 1-1/4" after the PRV.

 

[Sponsor]

 

[Reach4]

10 gpm.

 

[Curious Skip]

I'm going to piggyback on this post, because OP's setup is nearly identical to mine, as far as the number of fixture units, as well as the rental unit.

I installed a whole house filter this summer, and now the tenant has complained about a pressure drop while using the shower. He reported it as a fall-off during the shower, like we opened a valve on our end that drained off too much water. Usually there is no problem. The apartment is at the far end of the house, with a run of about 60 feet, and most of our fixtures branch off this line before it gets to the apartment. He gets what's left over.

Our supply from the city is 3/4 inch, with a pressure reducer installed. It enters the house at the opposite end from the apartment.

So, my question is this - Would it be worth it to branch off before the filter, and run a dedicated line to the apartment? I would need to install another filter for the apartment.

 

[Reach4]

So, my question is this - Would it be worth it to branch off before the filter, and run a dedicated line to the apartment? I would need to install another filter for the apartment.

I think yes.

You could do pressure drop measurements, but having a separate filter feeding the other apartment sounds like a worthwhile idea. Measurements only needed if you like to track numbers.

You could consider a bypass around the filter. You could consider a 3-valve bypass, which would let you maintain water flow while changing the cartridge. But you need to somehow relieve the pressure before unscrewing the housing. Some filters have a button for that.

 

[Jadnashua]

While you may have a decently sized inlet...what size pipe is run to the apartments? There are charts and calculators that you can use that will show the pressure drops with various diameter pipes at various flow rates. Distance, size, fittings, and flow rates all interact to drop both volume and pressure. Dynamic pressure is what you get with the flow occuring...that will change. Static pressure is with nothing running, and should be the same, so you need to know what the conditions are if you test things to get a valid indication of what's happening.

A whole home, building filter can severely affect the dynamic pressure if not sized properly or changed at the indicated intervals. It's not a bad idea to have a pressure gauge on both the inlet and outlet of the filter to help gauge how much pressure drop is occuring across it...when it rises too high, it's time to service the filter.

Note, a carbon filter that's not serviced properly can act like an infuser, putting stuff back into the line if it gets 'too' full of crud.

 

[Curious Skip]

You could consider a bypass around the filter. You could consider a 3-valve bypass, which would let you maintain water flow while changing the cartridge. But you need to somehow relieve the pressure before unscrewing the housing. Some filters have a button for that.

Checked all those boxes!

 

[Curious Skip]

While you may have a decently sized inlet...what size pipe is run to the apartments?

A whole home, building filter can severely affect the dynamic pressure if not sized properly or changed at the indicated intervals. It's not a bad idea to have a pressure gauge on both the inlet and outlet of the filter to help gauge how much pressure drop is occuring across it...when it rises too high, it's time to service the filter.

Note, a carbon filter that's not serviced properly can act like an infuser, putting stuff back into the line if it gets 'too' full of crud.

It's 3/4 all the way, with 1/2 secondary lines. If I proceed with this, I will probably include the gauges. I'm still trying to determine if it's really necessary. I opened a hose bib on that end of the house today, and it seemed to be fine. We're on city water, so this filter should last at least as long as the claim, which is 6 months or 50,000 gallons.
Thanks for the replies!

 

[wwhitney]

I opened a hose bib on that end of the house today, and it seemed to be fine.

If that hose bib is at the end of the line in the tenant's part of the plumbing, then a better test would go something like this:

(1) Get a hose y-splitter and a pressure gauge, and put them on the hose bibb. Measure the static pressure (no flow).
(2) Run water through the open side of the y-splitter (no other flow in the system) and measure the flow rate while reading the residual pressure on the pressure gauge.
(3) Repeat the last test while also filling a tub in your apartment.

Running a dedicated line to the other apartment, sized to match what you have now, isn't going to affect test result (2) significantly, unless the dedicated line is noticeably shorter or avoids the loss of a bunch of fittings in the current trunk. But it should improve the results of test (3).

And of course, to see what effect the filter is having on things, you can repeat tests (2) and/or (3) with the filter valves temporarily set to bypass. If doing that significantly improves (3), a dedicated line to the other apartment won't help as much unless it comes off before the filter.

Cheers, Wayne

 

[Curious Skip]

Lots to absorb here Wayne. I've gone down the YouTube rabbit hole looking for some info to help me understand what you said, but to no avail. What I'm stuck on is #2. How would I measure the flow rate? Is this where I would count the seconds to fill a one gallon bucket? Unless there's a restriction in the open port, the residual pressure on the gauge will be zero, or close to it.

 

[Reach4]

What I'm stuck on is #2. How would I measure the flow rate? Is this where I would count the seconds to fill a one gallon bucket?

5 gallon bucket, usually.

Then the gpm = (300/(seconds to fill))

 

[wwhitney]

Unless there's a restriction in the open port, the residual pressure on the gauge will be zero, or close to it.

The opening through the hose bib itself, and through the y-adapter's valve, will be a lot smaller than the inner diameter of even a 1/2" PEX water supply, so smaller than the pipe supplying the outlet. As such, the residual pressure on the gauge should be well above 0 psi.

If you did the test with a full port valve, then you may get a reading close to 0.

Reach4 answered your question about flow rate. I'd be more inclined to get/make a graduated container and time how long it takes to flow 1 or 2 gallons.

Cheers, Wayne

 

[Jadnashua]

How many apartments is the 3/4" line feeding? How many sinks, washing machines, showers, toilets are there in the complex? It seems small to me, but without knowing all of the things it needs to feed, can't say for sure.

 

[Reach4]

Reach4 answered your question about flow rate. I'd be more inclined to get/make a graduated container and time how long it takes to flow 1 or 2 gallons.

I was thinking you might flow for a timed interval, and use a bathroom scale to measure the weight of the water in the bucket. Then knowing the density of water....

 

[Curious Skip]

How many apartments is the 3/4" line feeding? How many sinks, washing machines, showers, toilets are there in the complex? It seems small to me, but without knowing all of the things it needs to feed, can't say for sure.

I checked Terry's link above, and counted my fixture units at 50. So it probably is too small, but it is what it is. The apartment (only one) only has the minimum number of fixtures; one shower, one toilet, one lavatory, one laundry, one kitchen sink, and the one hose bib. We (homeowners) have the majority of fixtures.

In talking with the tenant yesterday, I became aware that he is used to a higher pressure shower head, and we have the much softer feeling "rain head" installed. There may be no real problem at all.

 

[Reach4]

In talking with the tenant yesterday, I became aware that he is used to a higher pressure shower head, and we have the much softer feeling "rain head" installed. There may be no real problem at all.

In your tenant's mind, the pressure rises and falls due to use outside of the apartment. I suspect you can see how that might irritate you, but I expect it would irritate me.

 

[Jadnashua]

People confuse the output of a shower head with pressure, when it is much more a function of the velocity. By design, a rain shower head does NOT increase the velocity of the water, so it essentially dribbles out from the numerous outlets. A nozzle with a restriction causes the fluid to accelerate.

Take a hose, without a nozzle on it. Turn the water on. Point it up. See how far up it goes. It goes a certain height because of both the pressure and the velocity. Now put a nozzle on it and note how high up it goes. The pressure from the supply is identical, but because the nozzle creates a restriction, it goes faster. That's the same thing that causes a jet engine to produce thrust, or a carburetor jet to squirt gas into the system, or for a shower head to accelerate the water coming out.

 

[Curious Skip]

In your tenant's mind, the pressure rises and falls due to use outside of the apartment. I suspect you can see how that might irritate you, but I expect it would irritate me.

Yeah, for sure. So, I've been away for a few days, but on my return, washing a load of laundry, I asked the tenant to turn his shower on and try to note how much flow was lost when I started the washer. He said it fell off by "about a third". That's not acceptable.

Now for a solution.

This is the incoming line serving the whole house including the apartment. What I think I want to do is build up a copper manifold starting at the pressure relief valve, eliminating several PEX fittings. This would run about 8 feet, where I would tee off for a dedicated line to serve the apartment. I would then connect the PEX serving our living space to the new manifold. The run to the apartment will be about 50 - 60 feet, so I think I should use a roll PEX to minimize the number of fittings.

As I was typing the above, it dawned on me that I might be creating an imbalance that would give the apartment better flow characteristics so the apartment would draw pressure away from our space. I don't know! Any thoughts would be appreciated!

 

[wwhitney]

If you're going to rework that water entrance, I would think you'd want a hose bibb before the PRV so you can easily measure the incoming pressure, and a hose bibb with drain after the PRV for aiding in adjusting the pressure. [When lowering the downstream pressure, you have to relieve the pressure before taking a new reading.]

Also, if the filters could handle the high water pressure, they could go before the PRV, which should (I think) give you better pressure under flow after the PRV. I'm not sure if that's an arrangement that is ever used, or if it's problematic for some reason. Also, if you have some locations that want pressure reduced, unfiltered water, then you'd end up needing two PRVs.

Those issues aside, it make sense to just cut in a tee after the PRV and run a 1" PEX line over to the other apartment. That could just go to a new tee cut in somewhere in that apartment's distribution. That would leave you with a loop in the cold water line, which is fine and gives less pressure drop, but could be a bit confusing as far as shutoffs. So you'd want a ball valve at the supply end of the new run, and perhaps a ball valve in the current supply line to the apartment. The latter you could leave turned off if you want to avoid a loop.

As for impact on water pressure in your part of the house, that's certainly a possibility. Any water draw by the apartment will cause pressure drop on whatever piping and equipment is common to both units. Currently the apartment's water flow rate is limited by the long smaller run to it, and with the separate bigger run, it may draw more water through the common piping, dropping your pressure some. I don't think it's going to be a large effect, certainly it shouldn't be as bad as what the apartment user currently is describing. If you're concerned, you could install a throttling valve (globe, I think? I forget) on the new line. Then if you start having the opposite problem, throttle it somewhat for a better balance.

Cheers, Wayne

 

[Jadnashua]

Note, not all PRVs are created equal...some will flow more volume than others. You'd get more volume to that apartment if you t'ed off before the PRV and used anther one for him.