We have an old Valley (pre-1993) tub/shower faucet. After an outside line was repaired, we opened the cold water to flush the line, and dirty water came out, then the water pressure dropped and now there is no water at all. When the cartridge is removed, water shoots out with lots of pressure. Plumber who fixed outside line said valve in wall will have to be replaced, as cold water line must be clogged and hot and cold pressure must be there for water to flow.
Does the old Valley faucet really have a pressure valve in the wall?
Any suggestions?

Does the old Valley faucet really have a pressure valve in the wall?
Some shower valves do have a pressure balancing spool. They date back to about the 1993 era. If yours has one it will be on the cartridge not inside the valve.

After an outside line was repaired, we opened the cold water to flush the line,
Where, the outside hose bib or the shower?

After an outside line was repaired
Does that mean a hose bib was replaced or does it mean repairs were made to the line itself inside the house.

When the cartridge is removed, water shoots out with lots of pressure
Hot or cold or both? If only one was checked, why wasn't the other.

Does the old Valley faucet really have a pressure valve in the wall?
It may or may not but it won't be inside the wall.

Any other places where you don't have water?

The repair was to the water line coming into the house from the street. The drought down here has caused houses to shift and break lines - ours was broken right next to the house at the connector.

We flushed the cold water line to avoid the repair dirt from getting into the hot water heater.

The water coming from the faucet (after the cartridge was removed) was hot water. When theater was off, we tried blowing into both of the holes in the valve using a plastic line, but only hot water would come out.

All other water faucets are fine.

Update: We just replaced the cartridge, and now have hot and cold water from the cartridge, but the water pressure is very low - less than it was this morning before all this started! Maybe we partially dislodged something trying to get the old valve to work.

OK, look between where the repairs were done and the shower cold water line. Are there any stop valves?

No stop valves between repair and shower cold water line can be seen - but the pipes are in the slab.

The shower valve must have integral stop valve. If it doesn't removing the cartridge and turning on water should have blown blockage out. Remove faucet handle and cover plate, look in wall.
Do you see a fitting on either side on the incoming hot and cold water lines that can be turned with a flat blade screwdriver.

Do you have an access panel on the other side of the wall?

The shower valve does not have the fitting that would be turned with the flat blade screwdriver, Here's the picture of the assembly: http://www.plumbingsupply.com/vashosin.html

We have somehow fixed it, though - the last thing we did was hook up an outside water hose to the tub spout (using a connector) after blocking off the shower spout. It didn't sound like any water was moving through the faucet, but something must have been dislodged.

We now have full water pressure again.

Thanks for working with me on this.

One other thing that I would say remove the shower head and see if there is any dirt, clean and install, Thanks.

John

Congratulations Linda and thanks for the update.

Just so you know, what ever was blocking the valve was not dirt, it had to be either a small pebble or solder. It is still in the pipe and will most likely come back. Maybe tomorrow, next week or five years from now.

In my opinion the plumber should have fixed this. I am assuming the pipes were flushed through the tub and should have been flushed through an outside hose bib or through some valve that could have been easily removed.

It could have been something like a pebble but is more likely solder. If you use too much solder when soldering pipe the excess melted solder runs inside the pipe. When it hits cold pipe it solidifies but does not stick to the pipe. The water then carries it to the next available valve. Because the valve ports are smaller than the pipe, it gets stuck there blocking the valve.

Hope that it is many years before it comes back.

The older valley 2 handle tub faucets valve bodies can become partially or totally blocked due to the body design. When the water passes through the stem when you turn on the separate hot or cold handle the water has to pass through a thin slit type opening to get to the tub spout, this can be blocked by water heater sediment, disintegrating water heater dip tube, debris from the water main, etc. the valve should be updated to a modern pressure balance valve at this time because there's not a tool made to clean out this slit, odds of flushing are usually futal, hope this helps, craig the plumber.