Low DHW pressure after changing recirculating pump

[Luc]

Changed the recirculating pump for DHW because the original pump was too strong. We had several leaks in the elbows over the years. After investigating, we found that the water was circulating to fast in the 1/2'' return pipes.

The original pump was a Grundfos UP15-18SF and the new pump is a Grundfos UP15-B7. There are 3 supply lines of 3/4'' with returns of 1/2'' copper tubing.

After changing the pump, there is one faucet, at the end of one of the supply line, that really has low water pressure. The pressure of DHW elsewhere is fine. Any idea what can be done to increase hte DHW pressure at this faucet.

Kind regards,
Luc

 

[Patrick88]

After changing the pump, there is one faucet, at the end of one of the supply line, that really has low water pressure. The pressure of DHW elsewhere is fine. Any idea what can be done to increase hte DHW pressure at this faucet.

Is it low water pressure or low hot water pressure? If it is low water pressure check the aerator. That could have some debris in it

 

[Sponsor]

 

[Luc]

It is only the domestic hot water that is low pressure. The cold water at the faucet is fine. We checked the faucet and everything is ok there. I was thinking that there might be something obstructing the hot water pipe going to the faucet.

 

[Jadnashua]

ANy checkvalves in this system? Likely with a pump. Is it possible the circulator is pushing against the check valve (i.e., installed backwards)?

 

[guycol]

Stand your ground

Not plumbing answer but important.
If we all stood our ground and refused to give our SS# the problem would go away as with refusing to press one to speak English.
Now back to plumbing.

 

[Luc]

I don't think it is a check valve problem because all other faucet on the same run have good DHW pressure.

The low DHW faucet is the fartest away. Could it bee that the previous recirculating pump was contributing to a higher hot water pressure at this faucet? Will increasing the size of the DHW tubing going to this faucet increase the water pressure?

 

[Jadnashua]

People often confuse volume and pressure. Pressure in a static system (i.e., with no valves open) will be essentially the same everywhere. But, if you have a soda straw verses a fire hose, at the same pressure, you'll get a lot more water out of the fire hose. What you are referring to as a loss of pressure could easily be something clogging the valve or shower head, or aerator screen, reducing the volume by making it look like a smaller pipe. The length of the pipe and the friction associated with it can reduce the flow (volume) but won't affect the pressure. Larger pipes or ones with fewer connections (elbows) will have less friction, so provide more volume. If this all worked okay before, something has reduced the flow rate...crud caught somewhere.

If you have a huge demand, and your supply is small, then the supply might not be able to keep up and you'd see both a drop in pressure and a decrease in delivered volume expected at each port. Think poking one pinhole in the bucket verses shooting it with buckshot.

 

[Luc]

Thanks for the reply and explanation.

The flow rate is reduced. It takes more time to fill the sink. I will check the tubing to see if anything is clogging it up. If this does not do, I will see if we can increase the size of the tubing for this faucet.

Thanks.