cold water pressure on 1991 unihome u300

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cold water pressure on 1991 unihome u300

November 05, 2011, 05:20:28 pm

Hope somebody can help as my brain has now fried. We have a strange problem with the cold water pressure to all taps and toilet. What makes this a strange problem is that hot water pressure seems fine. It is the same whether using pump or city water. I can only imagine it is a scale build up. Has anybody any ideas? Please, please, please. Thank you
Liz & Andy. In UK

Re: cold water pressure on 1991 unihome u300

Reply #1 – November 05, 2011, 05:47:23 pm

Andy, Source of water for the pump is the same for both cold and hot. Water comes from the storage tank and then into the pump that pressurizes the whole system. If no pressure or low pressure on cold side in all outlets there must be an opening somewhere. Check the water fill in the water bay, if check valve is bad water will come out there,Check water drain valves in water Bay under water heater. check fill valve under the bathroom sink These have a habit of leaking back. Look everywhere for a cold water leak.
Good Luck
Gary B

Re: cold water pressure on 1991 unihome u300

Reply #2 – November 05, 2011, 06:02:22 pm

Hi Liz and Andy,

Looks like the translator is doing a good job as your words are coming out at this end fine.

OK, how about the pump. When you switch it on, does it pump normally and shut off? If you use the bathroom sink, is there more pressure/volume out of the hot water? When you leave the cold water faucet on, does the pump cycle on and off normally? There may be a valve partially shut off on the cold pressure line somewhere. Could be in the compartment where the pump is located.

Anyone else know about a shutoff valve in the cold pressure line?

Re: cold water pressure on 1991 unihome u300

Reply #3 – November 05, 2011, 06:16:33 pm

I havent seen any leaks and pump pressurises system ok as stops running. Another thing that happens is that water comes out of tank filler pipe when I remove the nonreturn valve that someone fitted to the filler maybe some of the pressure is getting back in the tank

Re: cold water pressure on 1991 unihome u300

Reply #4 – November 05, 2011, 06:26:02 pm

How about the fill valve hidden in the bathroom sink compartment? Is it shut off all the way?

My fill hose valve does leak back quite a bit when I pull the hose off. Stops naturally when I screw in the plug in the end of the line.

Re: cold water pressure on 1991 unihome u300

Reply #5 – November 05, 2011, 06:32:39 pm

I'm just guessing at most of this but will take a look tomorrow at my U300 if the rain stops to see if I can find a valve anywhere. Only other thing I could think of is a previous owner installing a filter in the cold that has become partially clogged.

Re: cold water pressure on 1991 unihome u300

Reply #6 – November 05, 2011, 06:49:13 pm

Yes pump stops running when faucets are closed. When just using cold water, pump is struggling and not running very fast at all. When I move faucet to hot the pump runs faster. Filler valve is definately closed. We have been hooked up to city water all summer and problems just started after filling tank to get ready for winter. So I am guessing some dirt has come out of tank. Where do you think it would be most likely to get blocked?

Re: cold water pressure on 1991 unihome u300

Reply #7 – November 05, 2011, 06:54:03 pm

Does anybody have any diagrams of plumbing on u300 that may help a lot. Could I blow air down a faucet to maybe unblock?

Re: cold water pressure on 1991 unihome u300

Reply #8 – November 05, 2011, 07:00:14 pm

Have you check the screen/filter on the pump inlet? It should affect cold and hot the same amount, but sure worth a check.

Brett

Re: cold water pressure on 1991 unihome u300

Reply #9 – November 05, 2011, 07:13:20 pm

Again, guessing but it would seem that if all the cold faucets experience the same problem, the partial blockage must be right after the pressure tank outlet splits to the hot water heater and the cold to the rest of the outlets. Since the pump and hot water heater come off of the water tank, I can't see the problem being in the water tank, pressure tank or pump. Blockage must be in the pressurized cold line before it hits the manifold that splits it to all the different faucets. So, I would find the pressure tank and the short line going to the cold manifold. Could be something small in the line or a rubber washer that has expanded from age and is partially blocking the line. The pump is probably running slower on cold because less water is flowing.

Would hold on blowing down the line until the cold routing can be mapped out.

Will try to look tomorrow at my U300 and foto the lines if possible.

Looks like a little after midnight your way.

Cheers,

Pierce

Re: cold water pressure on 1991 unihome u300

Reply #10 – November 05, 2011, 07:55:14 pm

Thank you all for your input, I will check out some of your suggestions tomorrow as bedtime for us now. What a forum, amazing you all so helpfull. Thanks again.
Andy&Liz

Re: cold water pressure on 1991 unihome u300

Reply #11 – November 05, 2011, 08:04:06 pm

Quote

I havent seen any leaks and pump pressurises system ok as stops running. Another thing that happens is that water comes out of tank filler pipe when I remove the nonreturn valve that someone fitted to the filler maybe some of the pressure is getting back in the tank

That is a major clue. No water should come back out of filler fitting. Sounds like back flow fitting is failing to seal. Could be after long term hooked up to city water may have affected check valve. Put a properly threaded plug in the filler fitting as a temp measure, if that solves it then replace the backflow valve ( also known as a check valve ).
Good luck
Gary B

Re: cold water pressure on 1991 unihome u300

Reply #12 – November 05, 2011, 08:17:15 pm

Any ideas where I would find this check valve?

Re: cold water pressure on 1991 unihome u300

Reply #13 – November 05, 2011, 09:43:46 pm

The check valve is internal to the female fitting into which you attach the shore water hose.

Re: cold water pressure on 1991 unihome u300

Reply #14 – November 06, 2011, 12:30:21 am

Quote from: rvcoupleuk – November 05, 2011, 06:16:33 pm

I havent seen any leaks and pump pressurises system ok as stops running. Another thing that happens is that water comes out of tank filler pipe when I remove the nonreturn valve that someone fitted to the filler maybe some of the pressure is getting back in the tank

If the hose bib has been changed, the new one may not have a check valve. If so it is normal that water runs back out until the plug is screwed in.

I can think of no reason that the cold water does not work when the hot water does. It almost has to be a pinched or blocked cold water line. Depressurizing the system by opening the fill valve and blowing the cold water through a faucet makes sense to me. Be sure to not exceed 40 psi air pressure. I would also open the city water bib to allow the air pressure to escape the tank. I am not aware that there is a valve that shuts off only the cold water.

Re: cold water pressure on 1991 unihome u300

Reply #15 – November 06, 2011, 09:30:27 am

If you find a piece of flexible tubing or hose on the cold water side of the plumbing after the water pump, it is possible that it has collapsed internally creating a restriction. That sometimes happens with rubber or plastic hose that has a woven reinforcement. Seems improbable that it would happen with a line under pressure, but it does.

Re: cold water pressure on 1991 unihome u300

Reply #16 – November 06, 2011, 04:14:26 pm

And assuming it's PEX tubing, check the aluminum bend-formers on the cold side to see if the PEX has slipped out and kinked. Is there a ManoBloc-style distribution manifold? If so, check the cold water inlet plumbing for plugged screens, gaskets plugging the line, etc.

Re: cold water pressure on 1991 unihome u300

Reply #17 – November 08, 2011, 06:12:05 pm

Liz & Andy,

Sorry for the delay but first day of sun without projects to do.

I took a couple of shots and tried to label the parts, direction of flow, etc. I think if you open the cold drain valve (labeled and the left drain of the two at the right side of the compartment) and at the same time, close the hot water heater shutoff (white valve), you may be able to blow the obstruction out. It would seem to me the partial blockage is above the "T" that goes to the white shutoff valve. After closing the white valve, you might unscrew the white fitting and if there is a blockage, it might come out there when you blow air in system. Don't use too much pressure.

Noticed the "white valve" may not be a shutoff as it seems to have another connection on the top.

I pushed the camera in under the water heater so the shot is looking up almost at the back of the compartment where the main tank is. Looks like it came out OK with most of the tubing visible. You can see where it starts to "T" off at the top of the compartment. Using a mirror and a light, you can see the same view in yours and check for kinks, damage, etc.

You may want to pull the carpeted panel off to the left of the water heater and take a look where the tubes come out of the water heater compartment.

Hope you get it figured out soon and that this helps.

Best,

Pierce

Re: cold water pressure on 1991 unihome u300

Reply #18 – November 09, 2011, 05:02:51 am

Firstly I would like to thank you all for your contributions they have all been very useful. Unfortunately the problem turned out to be scale build up. Yesterday I run kettle descaler through the pipes (probably not best practice) and managed to get bathroom sink and toilet working better than ever but shower and kitchen sink still need work.

Re: cold water pressure on 1991 unihome u300

Reply #19 – November 09, 2011, 08:48:49 am

Had a calcium scale buildup this past February. Had to take all the facets and valves that had screens apart and clean them. That included the toilet valve. It was not as bad of a job as I originally thought it would be. I had tried cleaning the system with vinegar, but that did not work. Think I could not get enough undiluted vinegar into the system.

Re: cold water pressure on 1991 unihome u300

Reply #20 – November 09, 2011, 11:29:57 am

Andy and Liz, I know this sounds stupid but Did you take the screens off the faucets and clear out the calcium deposits ? And while you are at It remove the shower head and soak it in vinegar. Sometimes the simplest things are the easiest to overlook. If you have a water filter under the sink it needs changed once in a while, more often in areas with contaminated or calcium rich water.
Good Luck
Gary B

Re: cold water pressure on 1991 unihome u300

Reply #21 – November 10, 2011, 10:45:59 pm

Andy & Liz,

Welcome to our Forum from a fellow Brit. I am not surprised that you have all that calcium build-up in the water system as the water is pretty hard where you live. Strange thing it did not affect the water heater though.

Good luck with the coach, it must be a pretty rare bird over there.

Keith & Joyce

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