Low to No Hot Water Pressure After Changing Whole House to Pex

[Canscrap4u2]

Two weeks ago we preemptively replaced every manifold and non-pex connection in our home with pex connections, after three floods. We also asked the plumber to replace all three shower heads and on tub faucet. We have extremely hard water. Have a well, a water softener and a recirculating tankless water heater. Immediately after the work was completed (21 holes in the walls), our water pressure was significantly lower. We can no longer take two showers at once or fill a tub and run the dishwasher as we could before. I would think, with new fixtures and no corrosion (10 year old home) that we would have more pressure not less. Plumber came back today and explains that new fixtures are placing higher flow demand on WH and the tankless is working hard with the temp of the well water to maintain demand. I mean literally our shower was at a dribble while I was filling the tub. We live in Oklahoma. This is our fourth winter with the tankless WH and have never had a decrease in hot water pressure due to cold temperatures before. We’ve had much colder temps than it is right now. I understand what he’s trying to say and he explained the pressure sensor to me on the tankless, but I just feel like we are missing something. It was so sudden, and we have literally created another problem by trying to avoid another one. Also he said really he should have installed a second tankless four years ago for the master and that if we did that we wouldn’t have this problem at all. ‍ Does anyone have any idea of anything else it could be or anything that We all have could be overlooking?

 

[Jeff Handy]

Maybe your tankless heater needs flushing, and the filter or filters could be clogged from crud in the system knocked loose during your repipe.

Also, there could be a check valve in the
circulator that could be clogged up.

Your softener inlet screen could be clogged.
The opening there is usually very tiny.
Try it on bypass to see if pressure comes way back up.

If you have a whole house filter, change the cartridges there.
Or try it on bypass also, for a test.

Is there a way of checking the water flow immediately before and after the tankless heater?
To see if there is a big restriction coming from there?
Not pressure, but volume of flow.

Check for any valves anywhere that got partially choked back during the repipe.

 

[Geofd]

Have you checked you mixinf valve......i had something like this on a newer wall hung boiler i soaked the mixing valve in vinagar for a while and it worked fine

 

[Diehard]

There are a lot of potential areas that could be blamed.

To begin with you say, "our water pressure was significantly lower." But neglect to clarify whether it applies to both Hot and Cold systems.

Pipe size changes between before and after and or different routing?

The system that was changed, namely the piping, we know nothing about.

Is it limited to the Hot water systems only, as implied?