pump supplies too much water pressure for hot shower

[Issanman]

I rented a new house with a Hitachi WM-P150XS water pump installed alongside of a 700 litre water tank. The water pressure is way too much for the Sharp 3500 watt water heater to even begin to give hot water. The water heater is turned on to full hot and the water comes out only barely warm. No way to get hot water with the pump running.

Is there any way to adjust for lower water pressure so that I may enjoy a hot shower on these cool mornings?

Or do I need to buy a larger water heater that may be able to heat the water that is blasting through the shower?

Turning down the water pressure at the shower just causes the pump to cycle on and off every 10 seconds or so.

 

[bankruatsteve]

Most installations will have a path for the water mains to circumvent the tank/pump by turning a valve or two.  But, if you don't have that, the pump cycling is normal with a low flow draw.  When it gets cold like this, the best 3500 watt will do is get the water warm on a very low flow rate.

[Kwasaki]

Change it over for a 7000 watt and put back the 3.5 when you vacate the house.

Just make sure it's earthed.

Edited December 20, 2017 by Kwasaki

[bankruatsteve]

2 minutes ago, Kwasaki said:

Change it over for a 7000 watt and put back the 3.5 when you vacate the house.

Just make sure it's earthed.

Except it's likely the current shower is wired with 2.5mm2 on a 20 amp breaker and 7Kw would need 6mm2 on a 32 amp breaker.  He could go to 4500 watt on 2.5mm2 but probably still not get a HOT shower.

[Kwasaki]

3 minutes ago, bankruatsteve said:

Except it's likely the current shower is wired with 2.5mm2 on a 20 amp breaker and 7Kw would need 6mm2 on a 32 amp breaker.  He could go to 4500 watt on 2.5mm2 but probably still not get a HOT shower.

Well if that's the case in the wiring in a new house I'd run another cable, I don't like cold showers. 

[Issanman]

I did try bypassing the pump/tank, but then the water pressure is too low to even trigger the water heater.

That would probably work in the middle of the night when everyone is asleep and not using mains water.

I was hoping that the pump would have an adjustment for turning down the maximum pressure. 

Thanks for the advice.

[bankruatsteve]

18 minutes ago, Issanman said:

I did try bypassing the pump/tank, but then the water pressure is too low to even trigger the water heater.

That would probably work in the middle of the night when everyone is asleep and not using mains water.

I was hoping that the pump would have an adjustment for turning down the maximum pressure. 

Thanks for the advice.

The pump probably does have a pressure adjust.  It's the one that says "DO NOT ADJUST".

[Crossy]

Don't mess with the pump.

 

Pump cycling 10 secs is fairly normal. I'm afraid you have to live with the pulsing pressure, or open another tap to get the pump on 100%

 

Right now our 6kW heater is struggling to get my morning shower to a temperature / flow rate that I like even in BKK 

[Issanman]

Opening another tap is an idea I already thought of and would almost certainly work, but not practical because of the wasted water, of course. 

So a bigger water heater seems to be the only solution.

I realize the wiring may need an upgrade first.

Thanks guys.

[wayned]

Most water heaters come with an adjustable plastic flow control valve that you are supposed to install on the input to the heater.  That way you can adjust the flow into the heater so that you get the temperature that you want.  Mine are controlled through the normal shutoff valve that I installed on the water outlet on the wall.  I have two or three of them out in the workshop.  Send me a PM with your address and I will send you one EMS - if I can find them!

[wayned]

12 hours ago, Crossy said:

Right now our 6kW heater is struggling to get my morning shower to a temperature / flow rate that I like even in BKK 

Yep, my 13 year old Sharp 6kw heater is "really" struggling to get the water warm enough now that the temp has dropped.  It's been getting a little worse each year most likely due to the deposit buildup inside.  Last year I bought a New Panasonic 4.5kw heater to replace it, but it wasn't needed in warm weather so it's still sitting in the workshop.  I never got "around to it", and now I'm freezing my butt off again!

[Crossy]

I'm not sure a flow reducer is going to help our OP. If he reduces the flow enough to get "hot" water the pump cycles.

 

Basic physics I'm afraid, baby water heater just hasn't got the oomph in the cool weather

 

Meanwhile I think I may be shopping for the 8kW version of our heater.

[wayned]

8 minutes ago, Crossy said:

I'm not sure a flow reducer is going to help our OP. If he reduces the flow enough to get "hot" water the pump cycles.

 

Basic physics I'm afraid, baby water heater just hasn't got the oomph in the cool weather

 

Meanwhile I think I may be shopping for the 8kW version of our heater.

The first unit that I bought was a 3.5 and the reducer certainly helped.  It might have caused the pump to cycle, I didn't notice a pressure fluctuation, but I did at least get hot water.  Now that it's cooler I have to turn the pressure way down, via wall mounted on/off valve, on my ancient 6kw to get good hot water.  I think that it's worth a try, free (I'll even pay the EMS charge) and easy to install, but agree that a 3.5 kw heater in Issan is probably too small.

 

An 8kw heater for a single shower room in Bangkok?  You must either want a steam room or possibly are getting old! Not really!

[lopburi3]

I am getting old but fine 3.5kw works here in Bangkok.  That type of pump is the issue - if you have a pressurized tank type it does not happen.  I get along with a 3.5kw heater here in Bangkok fine (even this week) buy turing the input water tap to heater lower - yes less flow but fine for the few days of cold weather we have in Bangkok.

[CGW]

On 12/21/2017 at 5:09 AM, Crossy said:

Basic physics I'm afraid, baby water heater just hasn't got the oomph in the cool weather

 

Meanwhile I think I may be shopping for the 8kW version of our heater.

I have a 8kw, barely noticed the difference between it and the 6kw that was replaced

Been cool up in Isaan past weeks, with water adjusted to minimum flow water still on the cool side!

 

[kelboy]

On Thursday, December 21, 2017 at 4:03 AM, wayned said:

Most water heaters come with an adjustable plastic flow control valve that you are supposed to install on the input to the heater.  That way you can adjust the flow into the heater so that you get the temperature that you want.  Mine are controlled through the normal shutoff valve that I installed on the water outlet on the wall.  I have two or three of them out in the workshop.  Send me a PM with your address and I will send you one EMS - if I can find them!

Correct, that's what I was going to say. 

[VocalNeal]

 

OP, you didn't say which model. Doesn't one simply adjust the flow using the valve bottom right together with the temp knob on the front? 

 

If there is a separate tap/faucet on the wall use that for on/off.

[Issanman]

It's a Sharp WH-A55 and it has no valve such as shown in the above picture.

 

[VocalNeal]

Weird. So then you will have to use the wall tap to reduce the flow.

[wayned]

4 hours ago, Issanman said:

It's a Sharp WH-A55 and it has no valve such as shown in the above picture.

 

The valves are usually included in the box but are not attached.  Whether you use it or not depends on the installation.  As I said in post #10, I have a couple of "extra" ones that I did not use.  Send me your address via PM and I will send you one via EMS, I'll even pay the shipping.  They are easy to install by just disconnecting the input hose to the heater and screw it to the heater and then the hose to the other end.  You would turn the pressure down until you get the desired temperature.  But, as said, a 3.5kw heater is stretching it in Issan and you might have to turn the flow way down to get what you want.

[VocalNeal]

6 hours ago, wayned said:

But, as said, a 3.5kw heater is stretching it in Issan and you might have to turn the flow way down to get what you want.

Oops missed that. They go something like 3.5, 4.5, 6.5 kW I asked why they said up north you need bigger. I decided on 6 kW even in BKK. If you buy an "electronic control" one it only uses enough power to maintain the desired temp. 

There are even 8kW and up but I think they are mainly for mixer tap installations.

Edited December 26, 2017 by VocalNeal

[lopburi3]

12 minutes ago, VocalNeal said:

 If you buy an "electronic control" one it only uses enough power to maintain the desired temp. 

Manual control does the same thing without additional components that add to cost and are likely to fail (been there).  How long do most of us have water running for a shower?  Running cost is really not that important for most I suspect as it is only a few minutes a day and when water turned off there is no cost.  Most of the year you will not be drawing anything like the full wattage for the period it is in use as the tanks of water we use do not require much increase in temperature.  Our AC/refrigerator/freezers are still the major electric users (unless cooking with electric).

Edited December 26, 2017 by lopburi3

[Issanman]

15 hours ago, wayned said:

 As I said in post #10, I have a couple of "extra" ones that I did not use.  Send me your address via PM and I will send you one via EMS, I'll even pay the shipping.  They are easy to install by just disconnecting the input hose to the heater and screw it to the heater and then the hose to the other end.  You would turn the pressure down until you get the desired temperature.  But, as said, a 3.5kw heater is stretching it in Issan and you might have to turn the flow way down to get what you want.

Yes, I am now sure the heater is too small. I will update to a larger heater so that I will be able to actually have a hot shower.

Thanks to wayned for the offer to send me the valve, but I think that it will not do enough to get some hot water until I upgrade the heater.

And thanks to everyone else for your advice and thoughts!

[lopburi3]

Having a hard time understanding - do you mean the heater just has an on/off control for water that you press to use?  It would be very easy to install one of these on the feed hose (should always have so it can be turned off) and use this to control the amount of water flow.

 

You are going to have the same issue with a larger heater if you have no way to control water flow - and you open to issue of enough electric supply to run it.

 

[Issanman]

There is a normal valve feeding into the heater from the wall. But when I adjust it low enough to get warm water, it causes the pump to constantly cycle on and off every 10 seconds or so, thereby changing the water pressure and the temperature of the water at the same time. Very aggravating!

[bankruatsteve]

The photo shows the temp control at mid-range.  Usually, there is a "sweet spot" with temp on max and water flow at a minimum but enough to have a shower.

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[canuckamuck]

Do you not have an air tank on your pump? You should not be noticing the pump cycling if you are simply using the shower. I mean the pump should cycle, but it should not be affecting the flow so noticeably.

For three years I had the same setup as you. A 150 watt pump and a 3500w shower heater. And where I live it gets down to 5 degrees sometimes. When it got cold we simply closed down the wall valve to the shower until the water would be warm. Yes it was very little flow sometime. But even though the pump would cycle, it had no noticeable effect on the flow from the shower. I think you have a pump problem as well as having a too small heater problem.

Maybe time to bleed the air tank.

 

[lopburi3]

22 minutes ago, canuckamuck said:

Do you not have an air tank on your pump? You should not be noticing the pump cycling if you are simply using the shower. I mean the pump should cycle, but it should not be affecting the flow so noticeably.

For three years I had the same setup as you. A 150 watt pump and a 3500w shower heater. And where I live it gets down to 5 degrees sometimes. When it got cold we simply closed down the wall valve to the shower until the water would be warm. Yes it was very little flow sometime. But even though the pump would cycle, it had no noticeable effect on the flow from the shower. I think you have a pump problem as well as having a too small heater problem.

Maybe time to bleed the air tank.

 

As he said in post one he has one of the constant pressure pumps without an air tank.  They either have to pump a lot of water and stay on or they cycle (and are often noisy as a jet aircraft with a solenoid louder than a 12 gauge shotgun).  Not pleasant living anywhere near them.

[canopy]

I've paid my dues using that type of system and it was constant trade off to find the most acceptable heat vs flow setting on a given day; always a case of robbing peter to pay paul. But now I have a 35,000 watt heater (not 3,500) since the shower head I have delivers an incredible 50 liters a minute and there are no longer any compromises. Boy is it nice to have a gushing shower that is steam hot on a cold day with thermostatic perfectly regulated temperature. Here is the secret for getting enough heat: use LPG (mine is), not electric. LPG always gives great heat no matter how bad your village wiring is. Another option to consider is you can install a hot water tank in line to your shower so that plenty of hot water is buffered and ready to go.

 

[Issanman]

The pump is a Hitachi WM-P150XS and I believe it has a very small air tank. And yes, it is very noisy.

The water pressure that it supplies is far more than we need. That's why I originally asked if it were possible to turn it down.

This is the first time I have had a pump on a house in Thailand and I don't much like it. But the city water pressure here is very low most of the time.

I once had a house in Florida with a well pump/tank setup but the air tank was about 5 feet tall.

I don't remember any problems with that setup, other than having to drain some water from the tank occasionally. 

This is a rental house, so I am looking to fix this problem without spending a lot of money. 

A bigger water heater is not so much money, and I can take it with me if I move to another place.