Stop and start water pressure to second cabin

[Daytona701]

Hi, I have 2 off grid cabins 70 feet apart with a 1700 gallon cistern and a Flotec 1/2 hp pump with bladder pressure tank. Pump is set to 30/50 with 28 psi. in bladder. Pump/pressure tank is in first cabin and pressure/flow is fine there. 1” pex is run between each cabin. The problem is at second cabin which is slightly downhill from first cabin. Water pressure/flow starts fine for about 60 seconds then stops for about 20 seconds then starts again for 60 seconds and continues cycle. Gauge at second cabin reads 30 psi when gauge at first cabin reads 40 psi. There is a 40 gallon propane water heater in each cabin. Problem started when cistern was run dry. Primed pump to restart water flow after cistern was filled by truck. I believe air may be trapped in line but need advice before cutting line and installing bleeder valve. Any advice will be greatly appreciated. Thank you.

 

[Valveman]

Doesn't make sense. If you have 30/50 at the first cabin and the second cabin is lower in elevation, you should be seeing 35 to 55 or so at the second cabin. Air would just get pushed out by the water. Do you have a clogged filter or a partially closed valve at the second cabin?

 

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[Reach4]

Water pressure/flow starts fine for about 60 seconds then stops for about 20 seconds then starts again for 60 seconds and continues cycle. Gauge at second cabin reads 30 psi when gauge at first cabin reads 40 psi.

Have you watched the gauge in the first cabin during a bad episodes in the second cabin?

I don't have a model in my head of what could cause the behavior.

 

[Daytona701]

The problem started when the cistern was run dry that is why I’m thinking there may be air trapped in the supply line. There is a shower, vanity, toilet and kitchen sink. I’ve opened all fixtures and run water for several minutes and the water runs normal then stops. The pump comes on after a delay and water flows again. I don’t know if trapped air could be causing the problem. All piping is pex and I was going to install a valve at the highest point to vent out any air. I will double check the shutoff valve. I installed the system myself in 2015 and haven’t had any problems until this one.

 

[Reach4]

I would guess this is a jet pump. You could have a submersible Flotec pump in the cistern, but I doubt it. Usually with a jet pump you want more than a 2 psi difference between the air precharge pressure and the cut-in pressure for the pressure switch. However that would not affect your main symptom. Having too much precharge would affect both cabins, and only for less than a second.

The pump comes on after a delay and water flows again. I don’t know if trapped air could be causing the problem

I suspect there is a check valve, that leaks, involved in this problem. Post a photo that includes the pump, pressure switch, and the wye that feeds pipe to cabin 2. I don't know how this would have only been triggered after the dry cistern, however.

If I understand correctly, somehow when the pressure at cabin 2 drops, the pressure does not drop at the pressure switch without a long delay. What could that many-second pressure differential? That is the question. As soon as the pump starts, is the pressure OK at cabin 2?

Air trapped in a line cannot cause this problem.

 

[Daytona701]

Just took a shower at cabin 2. About 60 seconds run with good pressure then 20 seconds no flow then 60 seconds run with good pressure. It’s a consistent cycle. There is a pump delay and as pressure builds water flow begins again. Will take pictures and post.

 

[WorthFlorida]

Is it only the shower? What about at the sinks? Anti scalding device in the shower valve may see the cold pressure drop to much so it tries to close off the hot water side, but not enough pressure to begin with. The shower valve should just close off one side or the other, not both but it’s something to look at. If if does not happen at the sinks, that should tell you it’s the cartridge in the shower.

As asked above, what does the pressure read at cabin 1 where the pressure tank is during this 20 second window? When the cistern ran dry, the pump may have picked up crud and it’s jammed up the shower cartridge. Remove the cartridge and clean it or replace it. It’s a try?

 

[Daytona701]

All fixtures are affected. When all fixtures are opened water flows normally then stops for about 20 seconds then starts again with normal flow and pressure. Time of on/off water flow cycle is consistent. Pump was sourced from local plumbing supply house. There is a check valve in the 1” line from the cistern to the pump. The pump is installed in the water heater closet at the rear of cabin 1. A 1” tee was installed about 3’ from the pump under cabin 1 with a run of about 70’ to cabin 2. 1” line enters water heater closet and supplies water heater then shower, toilet, vanity and kitchen sink. Water line is about 42” underground for freeze protection. Cabins are at 7600” elevation. Now when taking a shower you get wet, soap up when water stops and rinse when it comes back on. Have to be fast and probably saving a lot of water. Pisses off the wife though.

 

[Daytona701]

Will take pictures in the morning and post. Thank you for the help.

 

[Valveman]

The pump comes on after a delay and water flows again.

If this statement is correct it could cause your problem. When the pressure drops to 30 if the pump delays coming on for 20 seconds it would cause those symptoms. The pump should come on instantly when the pressure hits 30 and there will be no delay in water to the shower.

 

[WorthFlorida]

Since you read pressure differently between the two cabins, again I’m suspecting debris in the plumbing somewhere. With cabin 2 pressure dropping faster than at cabin 1, cabin 2 pressure drops enough for water not to flow. Is it a trickle or completely off? But the pressure at the pressure tank is above 30 psi so the pump doesn’t turn on. It’s taking about 2o seconds for water to flow past a restriction for the pressure to drop to turn on the pump. That leads me to believe there is a restriction between the cabins, at a tee or in the 1” PEX and it’s moving. With enough pressure the restriction is out of the way and as pressure drops it moves and blocks off the water. Same as squeezing a garden hose, plenty of pressure before the garden hose crimp, not much past it.

How to find it? Open the 1” pex pipe at cabin 1 and let the water flow, then try it at cabin 2 at the entrance. Is there a check valve or anti-backflow anywhere?